The Salisbury convention (or Salisbury doctrine) is a key constitutional convention that governs the relationship between the House of Commons and the House of Lords.

Its core principle is that the House of Lords will not vote against a government bill if the bill seeks to implement a commitment that was included in the governing party’s election manifesto.

The convention is a rule of political practice, not a law. It is based on the principle that the unelected House of Lords should not block the democratic will of the people as expressed in a general election.

The convention helps ensure that the Lords, while it has a duty to scrutinise and revise legislation, does not use its power to obstruct a government with a mandate to pass its legislative programme.

How does the Salisbury convention work in practice?

It is important to understand both what the convention does and what it does not do.

It prevents the House of Lords from rejecting a manifesto bill outright by voting it down at second reading (the main debate on the principle of a bill) or third reading (the final approval stage).

This ensures the bill is allowed to proceed through the legislative process.

However, the convention does not prevent the House of Lords from amending a manifesto bill. As such, the Lords retains its role as a revising chamber.

There is a limit to this revising power. The convention is also understood to mean that the Lords should not pass “wrecking amendments” – amendments that are designed to destroy or fundamentally alter the core purpose of the Bill as promised in the manifesto.

In May 2006, a joint parliamentary committee was created to consider codifying a series of constitutional conventions. It defined the Salisbury convention as follows:

“In the House of Lords:

“A manifesto Bill is accorded a Second Reading;

“A manifesto Bill is not subject to “wrecking amendments” which change the Government’s manifesto intention as proposed in the Bill; and

“A manifesto Bill is passed and sent (or returned) to the House of Commons, so that they have the opportunity, in reasonable time, to consider the Bill or any amendments the Lords may wish to propose.”

The origins of the Salisbury convention

The Salisbury convention has its origins in the political situation immediately following the 1945 general election. The election resulted in a landslide victory for the Labour Party and the appointment of Clement Attlee as prime minister.

The party was elected overwhelmingly on a manifesto, entitled Let Us Face the Future, which pledged radical social reform, including the creation of a new “National Health Service”.

Attlee, the first prime minister of a majority Labour government, faced a massive, inbuilt, hereditary Conservative majority in the House of Lords. The upper chamber was entirely hereditary and had few Labour peers.

To avoid constitutional gridlock, an understanding was reached between the Conservative Leader in the House of Lords, Viscount Cranborne (later the Marquess of Salisbury), and the Labour leader in the Lords, Viscount Addison. The doctrine has sometimes been referred to as the Salisbury-Addison convention (after Viscount Addison, the leader of the House of Lords at the time).

Responding to the 1945 king’s speech, Cranborne/Salisbury said that it would be “constitutionally wrong” for the Lords “to oppose proposals which have been definitely put before the electorate.” This principle has since been referred to as the Salisbury convention, therefore, or Salisbury-Addison convention (after Viscount Addison, the leader of the House of Lords at the time).

In his memoir, As It Happened, Attlee recounted his relationship with the Lords as prime minister. He said Labour experienced “no trouble” across its first three years in power after the 1945 election. Rather, the House of Lords “fulfilled a useful role as a debating forum and a revising chamber.”

The former prime minister referred to two exceptions to this rule: steel nationalisation and the Parliament Act 1949.

In 1964, Salisbury reflected on his relationship with the Attlee government. He said that due to the large Labour majority in the commons, Conservative peers adopted the “broad guiding rule that what had been on the Labour Party programme at the preceding general election should be regarded as having been approved by the British people.”

Salisbury added: “Therefore… we passed all the nationalisation bills, although we cordially disliked them, on the second reading and did our best to improve them and make them more workable at committee stage.

“Where, however, measures were introduced which had not been in the Labour Party manifesto at the preceding election, we reserved full liberty of action.”

Salisbury convention: modern challenges and application

The evolution of the convention

The convention’s application has been debated in the modern era. After the removal of most hereditary peers in 1999, some argued that the Lords had greater legitimacy and that the convention was less relevant.

In the wake of the House of Lords Act 1999 (which reduced the number of hereditary peers to 92), the Conservative leader in the Lords, Lord Strathclyde, argued that the House had “changed” and that it had a “new authority”.

Strathclyde called for parliament to “re-examine the Salisbury convention and for discussion to take place before a new agreement can be reached between the parties.”

However, the consensus remains that as long as the House is unelected, the convention should hold.

The 2006 joint parliamentary committee on constitutional conventions was created to consider “the practicality of codifying the key conventions on the relationship between the two Houses of Parliament which affect the consideration of legislation”.

The committee found that the convention had changed over time, stating: “We are persuaded by the strength of the argument that the Salisbury-Addison convention has changed since 1945, and particularly since 1999.”

Defining ‘manifesto bill’

The joint committee found that the convention applied to manifesto bills introduced to either House and was now recognised “by the whole House, unlike the original Salisbury-Addison convention which existed only between two parties [Labour and Conservative]”.

The committee also noted “the emergence in recent years of a practice that the House of Lords will usually give a second reading to any government bill, whether based on the manifesto or not”.

The relationship between the Houses has evolved in a way that the primacy of the commons infuses all aspects of the upper chamber’s work.

The cross-party group ultimately recommended against any form of codification that would “turn conventions into rules, remove flexibility, exclude exceptions and inhibit evolution in response to political circumstances”.

The convention’s application rests on the definition of “manifesto bill”. Proposed legislation is not clearly defined in a party’s election manifesto; the documents amount to long lists of pledges, some of which are more specific than others.

2010-2015 coalition: conventional challenges

The convention can be problematic during a period of minority or coalition government. The 2010-2015 Conservative-Liberal Democrat coalition government was formed as the result of a hung parliament, meaning no single party’s election programme was endorsed by the electorate. The two parties instead came together to produce a joint “coalition programme” document, which combined aspects of the Conservative and Liberal Democrat manifestos and embraced compromise measures in other areas.

A 2014 House of Lords select committee on the constitution report found that a coalition agreement did not have “status of a manifesto”. It therefore found that its commitments are not inherently “subject to the Salisbury-Addison convention.”

It added, however, that commitments contained in such an agreement that had previously appeared in the manifestos of parties making up the coalition “should be treated as subject to the convention.”

The committee stated: “We conclude that the Salisbury-Addison convention – whereby bills foreshadowed in a government’s manifesto are given a second reading in the Lords, are not subject to wrecking amendments and are passed in reasonable time – does not, strictly speaking, apply to measures in a coalition agreement. This is because a coalition agreement cannot be said to have a mandate from the electorate in the way that a manifesto can.

“However, if all parties in a coalition made the same or a substantially similar commitment in their manifestos, then they should be entitled to the benefit of the Salisbury-Addison convention in respect of that commitment.

“We recognise that a practice has evolved that the House of Lords does not normally block government bills, whether they are in a manifesto or not. There is no reason why this practice should not apply when there is a coalition government”.

During the 2010-2015 coalition government, peers tried and failed to block three government bills at second reading.

The 2017-2019 hung parliament and the Salisbury convention

The application of the Salisbury convention also emerged as a point of debate in the 2017-2019 hung parliament. Following the 2017 general election, the prime minister, Theresa May, backed down on a series of controversial manifesto pledges, including the so-called and much-maligned “dementia tax”.

In response, the Liberal Democrat chief whip, Alistair Carmichael, said he did not believe certain aspects of the government’s programme, set out in the 2017 queen’s speech, were covered by the Salisbury convention.

He said: “The government is not only going to struggle to gets its business through the House of Commons, it is going to have one hell of a job to get stuff through the House of Lords.”

At the time, the government argued that the Salisbury convention “applies to the manifesto commitments of the government, whether that is a majority government, coalition or minority government.”

Government lawyers argued that the convention would apply in relation to the 2017 “manifesto and the House of Lords.”

During the Brexit process, some supporters of the government argued that the Lords had passed “wrecking amendments” to legislation relating to Britain’s withdrawal from the European Union (EU).

The Parliament Acts of 1911 and 1949

The Parliament Acts of 1911 and 1949 are two crucial pieces of constitutional law that establish the legislative supremacy of the elected House of Commons over the unelected House of Lords.

The acts provide a legal procedure by which a proposed law (a bill) can become an act of parliament even if it is rejected by the House of Lords. They provide a constitutional “backstop” that ensures the will of the democratic chamber can ultimately prevail in the event of a sustained disagreement with the second chamber.

The power is used very rarely and only as a last resort when all attempts at compromise between the two Houses have failed.