A written constitution is a single, codified document that sets out the fundamental laws and principles by which a state is governed. It defines the main institutions of government, outlines their powers, and establishes the relationship between the state and its citizens.

The United Kingdom is highly unusual among major democratic nations in that it does not have such a document. The debate over whether the UK should adopt a written constitution is a long-standing one, though it has largely been confined to academic, legal and political circles with limited public traction.

Why does the UK not have a codified constitution?

It has been argued that written constitutions around the world have only ever come into being as a result of a climactic “constitutional moment”, such as a revolutionary event or national independence. Britain’s political and historical development has lacked a decisive “big bang” – comparable to the United States of America’s war of independence – that might have sparked the creation and sustained adoption of a single, codified constitutional document.

The idea of a codified constitution is not inherently identified with “left” or “right” in ideological terms. It can be framed either as forming part of a progressive project of modernisation, or, conversely, as a conservative measure designed to entrench British values and preserve the constitutional status quo.

Historically, however, the drafting and entrenchment of codified constitutions has been couched in the rhetoric of freedom and liberalism. The most common arguments against a codified constitution, which centre around parliamentary sovereignty and fears of judicial overreach, tend to be conservative in nature.

The current Labour government has no plans to introduce a written constitution. The previous Conservative government’s project to replace the Human Rights Act with a new Bill of Rights, spearheaded by former justice secretary Dominic Raab, was officially shelved in 2023.

The academic J. A. G. Griffith once argued that the UK “constitution is what happens… if it works, it’s constitutional”.

Key sources of the UK’s uncodified constitution

The UK’s constitutional framework is derived from a variety of sources, both written and unwritten, that have evolved over centuries. In its famous judgment ruling prime minister Boris Johnson’s prorogation of parliament unlawful in 2019, the supreme court referenced this reality.

The court stated: “Although the United Kingdom does not have a single document entitled ‘The Constitution’, it nevertheless possesses a constitution, established over the course of our history by common law, statutes, conventions and practice. Since it has not been codified, it has developed pragmatically, and remains sufficiently flexible to be capable of further development.”

Acts of parliament

Primary legislation, enacted through acts of parliament, represents the highest form of law and takes precedence over all other legal sources. Collectively referred to as the “statute book”, it comprises the full body of statute law currently in force and constitutes one of the most significant sources of the UK constitution.

Unofficially, major or “constitutional statutes” are seen to have especial significance. These include the Parliament Acts of 1911 and 1949 which established the supremacy of the House of Commons, the Scotland Act 1998 which created the Scottish Parliament, the Human Rights Act 1998, and the Act of Union 1707.

The royal prerogative

Royal prerogative powers are the residue of powers that were once exercised personally by the monarch. These powers are now almost entirely exercised by government ministers acting on the monarch’s behalf, providing the legal basis for a range of executive actions. They include the power to dissolve and summon parliament, and the power to declare war and deploy the armed forces overseas.

The royal prerogative is limited by reforms made under statute law, convention and oversight by the courts.

Judicial precedent (common law)

Decisions made by judges in senior courts can set precedents that define the rights of individuals and the limits of government power, forming a key part of constitutional law.

Constitutional conventions

These are unwritten rules of political practice that are considered binding but are not legally enforceable. Examples include the convention that the monarch will grant royal assent to any bill passed by parliament, despite technically having the power to refuse, and the rule that the prime minister must be a member of the House of Commons. In recent times, conventions have been set out in official but not legally-binding documents such as the cabinet manual and the ministerial code.

Authoritative works

The nature of the UK’s uncodified constitution means that expert interpretation plays a crucial role in shaping shared understandings and resolving ambiguities as they arise. These expert interpretations are set out in a body of literature known as “authoritative works”. Two key examples include: Walter Bagehot’s The English Constitution (1867) and A.V. Dicey’s Introduction to the Law of the British Constitution (1885).

Assimilated EU law

The European Union (Withdrawal) Act 2018 removed the provision that European Union (EU) legislation automatically took effect as domestic law in the UK. It transferred all EU law onto the UK statute book, creating “retained EU law” as a type of UK domestic law.

Under the Retained EU Law (Revocation and Reform) Act 2023, this body of law, now referred to as “assimilated law”, is no longer supreme over domestic UK legislation. This means that if a piece of assimilated law (former EU law) conflicts with a piece of domestic UK legislation, the UK law now generally takes precedence.

Historic charters

Documents such as Magna Carta (1215) and the Bill of Rights (1689) have foundational symbolic importance, establishing principles of limited government and the rights of parliament.

The leading English judge Lord Denning described Magna Carta as “the greatest constitutional document of all times – the foundation of the freedom of the individual against the arbitrary authority of the despot”. More recently, in 2005, Lord Woolf, then the lord chief justice, called it the “first of a series of instruments that now are recognised as having a special constitutional status”.

The case for a written constitution

Clarity and accessibility

Proponents argue that a single, accessible document would allow citizens to better understand their rights and the workings of government. They contend that the current uncodified arrangement is obscure, complex, and understood by only a small group of experts.

Limiting executive power

A key argument is that a written constitution is needed to restrain the power of the executive, particularly a government with a large majority in the House of Commons. Under the doctrine of parliamentary sovereignty, such a government can pass almost any law it wishes. A codified constitution could establish more robust checks and balances, preventing an “elective dictatorship”.

Protecting human rights

At present, individuals’ rights remain dependent on ad hoc statutory protection or upon judicial protection under common law. For instance, while the Human Rights Act 1998 protects fundamental rights, it is an act of parliament that could, in theory, be repealed by a simple majority vote. A written constitution could entrench these rights more securely, making them harder for a future government to overturn.

The case against a written constitution

Flexibility and adaptability

The primary argument against codification is that the UK’s unwritten constitution is flexible and can adapt to changing social and political circumstances without the need for rigid and often difficult formal amendment processes. It allows for organic, evolutionary change.

Parliamentary sovereignty

Opponents argue that a written constitution, interpreted by unelected judges, would undermine the core principle of parliamentary sovereignty. They contend that it is undemocratic for judges to have the power to strike down laws passed by the people’s elected representatives in Parliament.

An entrenched written constitution, in particular, would refute the convention that no future parliament can be bound irrevocably by the actions of a previous parliament – a principle that lies at the heart of the “orthodox”, Diceyan doctrine of parliamentary sovereignty.

Politicising the judiciary

A related concern is that a written constitution would inevitably draw the judiciary into political disputes. Judges would be required to rule on the constitutionality of government policy, potentially being accused of political bias and undermining their perceived neutrality.

Brexit and the UK’s uncodified constitution

Brexit placed significant strain on the operation of the UK’s uncodified constitution, giving rise to two major cases concerned with the exercise of the royal prerogative. In both instances, the supreme court intervened to prevent the executive from committing what it judged to be breaches of the UK’s constitutional arrangements.

Article 50 controversy

In 2017, the supreme court ruled that the government could not notify the Council of the European Union of the UK’s intention to withdraw from the EU (formally triggering the process set out in Article 50 of the Treaty on European Union) under the royal prerogative.

Gina Miller, a business owner and transparency campaigner, had brought the case before the high court in 2016, arguing that the executive could not use the royal prerogative to effectively nullify previous acts of parliament relating to European integration. The government, led in court by the attorney general, Jeremy Wright, maintained that the 2016 referendum result represented a clear mandate for the executive to exercise prerogative powers.

On 24 January 2017, the supreme court ruled by a majority of eight to three that because the European Communities Act 1972 had incorporated EU law, only an act of parliament could authorise its removal. Delivering the verdict, Lord Neuberger, the president of the supreme court, said: “Withdrawal effects a fundamental change by cutting off the source of EU law, as well as changing legal rights.

“The UK’s constitutional arrangements require such changes to be clearly authorised by parliament.”

Prorogation controversy

On 24 September 2019, the supreme court unanimously ruled that Boris Johnson’s request for Queen Elizabeth II to prorogue parliament was unlawful. Eleven justices, led by Lady Hale, ruled that the prorogation was “void and of no effect”, meaning parliament could be reconvened the following day.

The leader of the House of Commons, Jacob Rees-Mogg, had convened a meeting of privy councillors which advised the queen to prorogue parliament on 28 August 2019. The approach was denounced by critics, including those within the Conservative Party, as an anti-democratic, unconstitutional ploy to bypass MPs – at a time when the parliamentary arithmetic was finely balanced.

Prorogation in order to secure a ‘no deal’ Brexit – the default legal position under EU law’s Article 50 process – had been a point of debate in the recent Tory leadership contest.

In delivering its ruling, the supreme court noted its historical role in protecting “parliamentary sovereignty from threats posed to it by the use of the prerogative powers and in doing so have demonstrated that prerogative powers are limited by the principle of parliamentary sovereignty”.

The court added: “The sovereignty of parliament would, however, be undermined as the foundational principle of our constitution if the executive could, through the use of the prerogative, prevent parliament from exercising its legislative authority for as long as it pleased.”

The case for a codified constitution: a short history

In 1976, the former lord chancellor and Conservative peer, Lord Hailsham, popularised the term “elective dictatorship” to describe the United Kingdom’s system of government. Hailsham (formerly Quintin Hogg) argued that the existing unwritten constitutional framework contained too few checks and balances and needed overhauling.

In the 1980s, the Social Democratic Party (SDP) and Liberal alliance endorsed the idea of a written constitution. The SDP-Liberal alliance’s manifesto for the 1983 election, Working Together for Britain, argued that the UK had rested “on our laurels as the oldest modern democracy” and grown “smug and complacent with the result that the rights we have taken for granted are being increasingly threatened.”

The party called a series of measures to “buttress our now shaky structure of liberties and rights and guarantee them by law”, including a new bill of rights.

The Liberal Democrats (the product of the SDP-Liberal merger) continue to support this position. The party’s 2024 manifesto called for “the creation of a UK constitutional convention, with the aim of drafting a new federal constitution”.

In 1990, the Liberal Democrats became the first major UK political party to publish a fully drafted, article-by-article proposal for a written constitution. The party’s 79-article draft document, entitled ‘We, the People’ – Towards a Written Constitution, proposed a federal UK, a proportional voting system, an elected upper chamber and a supreme court.

In June 1991, veteran Labour MP Tony Benn introduced the Commonwealth of Britain Bill, which called for a constitutional overhaul and codification. The bill proposed abolishing the monarchy and the House of Lords, fashioning a “house of the people” to replace the upper chamber, disestablishing the Church of England, and establishing a new “Commonwealth of Britain” with a president serving as head of state. It also called for lowering the voting age to 16, a federal framework, and granting the constituent nations of the UK a right of secession. The bill was seconded on introduction by the future Labour leader, Jeremy Corbyn.

Benn reintroduced the bill on several occasions before his retirement in 2001.

In 2007, the Labour prime minister, Gordon Brown, shifted toward supporting a written constitution. In a statement to the commons on constitutional reform, Brown argued that there was a case to “codify either in concordats or in a single document both the duties and rights of citizens and the balance of power between Government, Parliament and the people.”

He added: “In Britain we have a largely unwritten constitution. To change that would represent a fundamental and historic shift in our constitutional arrangements.

“So it is right to involve the public in a sustained debate about whether there is a case for the United Kingdom developing a full British Bill of Rights and duties, or for moving towards a written constitution.”

In a statement to the commons in June 2009, Brown declared: “I personally favour a written constitution”.

Brown thereby became the first prime minister to endorse the principle of a codified constitution.

In February 2010, Brown called on the cabinet secretary, Sir Gus O’Donnell, to lead efforts to “consolidate the existing unwritten, piecemeal conventions that govern much of the way central government operates under our existing constitution into a single written document”.

The Cabinet Office subsequently produced a draft cabinet manual in December 2010, which was later approved and published by Brown’s successor as prime minister, David Cameron, in October 2011.

The opening paragraph of the cabinet manual states: “The UK is a parliamentary democracy which has a constitutional sovereign as head of state; a sovereign parliament, which is supreme to all other government institutions, consisting of the sovereign, the House of Commons and the House of Lords; an executive drawn from and accountable to parliament; and an independent judiciary.”

The cabinet manual has no legal force and does not resemble the formal codified constitutions found in other countries. Rather, it provides an account of the sources of the UK’s uncodified constitution and explains how those sources operate in practice. For instance, it describes the operation of several of the prerogative powers.

The cross-party House of Lords constitution committee concluded that the attempt to spell out the conventions underpinning how government works was not a “first step” to a written constitution.

The committee stated: “In our view the cabinet manual has limited value and relevance… we conclude that the manual is not the first step to a written constitution. It should be renamed the Cabinet Office manual and its greater relevance to officials than to politicians emphasised.”

The Labour’s 2010 manifesto included a commitment to create an “all party commission to chart a course to a written constitution.”

The Conservative-Liberal Democrat coalition government showed some enthusiasm for constitutional codification. The coalition agreement featured a pledge to “establish a commission to investigate the creation of a British bill of rights that incorporates and builds on all our obligations under the European Convention on Human Rights, ensures that these rights continue to be enshrined in British law, and protects and extends British liberties.”

In March 2011, the government launched the independent commission on a bill of rights. The commission’s report, published in December 2012, was titled A UK Bill of Rights? – The Choice Before Us.

Of the Commission’s nine members, seven believed that, on balance, there was a strong argument in favour of a UK bill of rights. However, two members, namely Philippe Sands QC and Baroness Kennedy QC, remained unconvinced and expressed concern over the potential implications of a domestic rights framework, which could see the UK de-couple from the ECHR. Two members of the commission who supported a British bill of rights advocated withdrawing from the ECHR.

The shadow justice secretary, Sadiq Khan, responded: “The commission was a classic political fudge, designed to paper over the cracks within the Tory-led government, and [the] report is a dog’s breakfast as a result.”

The lack of consensus did not provide a sustainable basis for legislative progress. The Conservative Party, however, remained attached to the idea and included it in their 2015 general election manifesto.

The manifesto stated: “The next Conservative government will scrap the Human Rights Act, and introduce a British bill of rights. This will break the formal link between British courts and the European Court of Human Rights, and make our own supreme court the ultimate arbiter of human rights matters in the UK.”

Britain’s departure from the European Union necessarily occupied much of the government’s constitutional bandwidth.

Then, in June 2022, the justice secretary, Dominic Raab, introduced a formal Bill of Rights Bill to parliament. This proposed to repeal the Human Rights Act 1998 and give legal supremacy to the UK supreme court and make it explicit that UK courts can disregard rulings from the ECHR.

Liz Truss, upon becoming prime minister in September 2022, initially shelved the bill. Robert Buckland, the secretary of state for Wales, had previously warned that the proposals to “elevate certain parts of our existing statute law” risked politicising the courts.

However, the bill was then resurrected during Rishi Sunak’s tenure as prime minister, who reappointed Raab to the post of justice secretary. In April 2023, Raab resigned after a bullying inquiry found he acted in an “intimidating” and “aggressive” way towards officials.

Raab’s successor as justice secretary, Alex Chalk, then announced the government would drop the bill in June 2023.

Chalk told the House of Commons: “Having carefully considered the government’s legislative programme in the round, I can inform the House that we have decided not to proceed with the bill of rights.”

He added: “It is right that we recalibrate and rebalance our constitution over time, and that process continues.”

Quotes

“As the British Constitution is the most subtle organism which has proceeded from progressive history, so the American Constitution is the most wonderful work ever struck off at a given time by the brain and purpose of man” – William E. Gladstone, 1878

“We will establish a Commission to investigate the creation of a British Bill of Rights that incorporates and builds on all our obligations under the European Convention on Human Rights, ensures that these rights continue to be enshrined in British law, and protects and extends British liberties. We will seek to promote a better understanding of the true scope of these obligations and liberties.” – The Coalition: Our programme for government, 2010

“The Bill of Rights will strengthen our UK tradition of freedom whilst injecting a healthy dose of common sense into the system. These reforms will reinforce freedom of speech, enable us to deport more foreign offenders and better protect the public from dangerous criminals.” – Dominic Raab, 2022, before the Bill of Rights was shelved

Additional resources

• Article: ‘Should Britain have a written constitution?’ by Vernon Bogdanor, Tarunabh Khaitan, and Stefan Vogenauer https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-923X.2007.00879.x