Primary legislation is the term used to describe the main laws passed by the legislative bodies of the UK. This type of legislation is also referred to as “statutes” or “statute law”.

Secondary legislation is delegated legislation made by a person or body under authority contained in primary legislation.

Once a proposed law (bill) has been passed by both the House of Commons and the House of Lords, and has received royal assent, it becomes an act of parliament and part of UK law.

All bills are categorised based on their scope and purpose. The three main types are Public Bills, Private Bills, and Hybrid Bills. Each category is subject to a different parliamentary process to ensure it receives the appropriate form of scrutiny.

Public Bills

Public Bills are the most common type of legislation. They deal with matters of public policy that affect the general population of the country, or a significant part of it. The vast majority of Bills introduced to Parliament are Public Bills.

To receive royal assent, a public bill must secure its first reading (formal introduction) and second reading (debate on the main principles), pass its committee stage (detailed clause-by-clause scrutiny), receive approval at report stage (further amendments), and, finally, achieve a third reading (final approval) – in both the House of Commons and the House of Lords.

There are two sub-categories of Public Bill.

Government bills

Government bills are introduced by a government minister and represent the government’s legislative programme. They make up the bulk of the legislation passed by parliament each year. An example is the annual Finance Bill, which enacts the budget.

Government bills often enact manifesto commitments and are typically outlined in the king’s speech/queen’s speech at the start of each new parliamentary session.

Private members’ bills (PMBs)

Private members’ bills or PMBs are Public Bills that are introduced by an individual MP or a member of the House of Lords who is not a government minister. These MPs are referred to as “backbenchers”.

While any backbencher can introduce a bill, very few become law due to the limited amount of parliamentary time allocated for their debate. They are, however, an important way for MPs to raise the profile of an issue.

PMBs may take the form of a “ballot bill”, which is a proposed piece of legislation tabled by a backbench MP who has been randomly selected from a ballot held at the beginning of a parliamentary session. These ballot bills are given precedence over other PMBs and so have a greater chance of becoming law.

Other PMBs include 10-minute rule bills, which are introduced under a special procedure, and presentation bills, which are simply introduced to the House. Presentation bills and 10-minute rule bills rarely progress beyond their initial introduction.

A high-profile example of a PMB is the Terminally Ill Adults (End of Life) Bill, which was introduced to parliament by Labour backbench MP Kim Leadbeater. The bill was introduced after Leadbeater was selected by the parliamentary ballot.

Private Bills

Private Bills are rare and should not be confused with private members’ bills.

A Private Bill is promoted and introduced by an external organisation, such as a local authority or a private company, to grant itself special legal powers that are not available under the general law. They therefore only change the law as it applies to that specific individual or organisation. For example, a local council might promote a private bill to give it the power to build and manage a new bridge or a specific transport system.

In the 19th century, a majority of legislation passed by parliament was private business – relating to public works, transport schemes and other settlements.

Private Bills process

The formal stages of Private Bills are notably different from those of a Public Bill.

• Firstly, the promoting organisation must first deposit a petition at parliament, along with a copy of the proposed bill. The promoter must also appoint a Parliamentary Agent to represent the case for the bill during its parliamentary stages.
• The examiners of petitions for Private Bills (parliamentary officials appointed by the speaker) then report on whether the bill complies with the relevant standing orders (House rules).
• The formal first reading of the bill follows in the originating House (commons or Lords).
• A period is then set aside during which any individual or organisation that would be “specially and directly” affected by the bill can submit a formal objection, known as a “petition against the bill.” Only petitioners who are “directly and specially affected” by the bill have the right to have their petitions considered by the committee on the bill.
• The promoter of the bill has the right to object to petitions if they believe the petitioner is not “directly and specially affected” by the bill. A “court of referees” is established in such cases to consider the rights of the petitioner. The court is made up of the deputy speakers, eight backbench MPs, and the speaker’s legal adviser.
• The second reading of the bill follows. At this point, parliamentarians may raise objections and seek to thwart its passage.
• Subsequently, if the bill is opposed by petitioners, it is referred to an “opposed bill committee”. This specially appointed committee has a quasi-judicial function, hearing evidence from the bill’s promoters and from the petitioners against it, who are often represented by legal counsel. The committee then decides whether the case for the bill outweighs the objections raised. (An “unopposed bill committee” is formed for those Private Bills which have not been petitioned against.)
• There are two possible outcomes. The case behind the Private Bill may be approved, allowing the proposed legislation to progress. Or it may be denied. The latter option is tantamount to rejection of the whole bill.
• If the case behind the bill is proved, the committee considers possible amendments in light of concerns raised by petitioners. The promoter of the bill may also propose amendments. The bill then progresses to its report or “consideration” stage in the commons, when any MP may propose amendments. It then progresses to third reading.
• The bill then goes through the same process in the House of Lords.

Due to this protracted process, Private Bills may be “suspended” at the end of a parliamentary session and resumed at the beginning of a subsequent session. Public Bills typically have to secure their passage in a single session.

Examples of Private Bills

The City of London (Markets) Bill is an example of a Private Bill. Submitted to Parliament by the City of London Corporation on 27 November 2024, the bill aimed to remove the Corporation’s statutory responsibility to operate the Smithfield and Billingsgate meat and fish markets. Property law firm Pinsent Masons described the meat and fish markets as “effectively fixed to the current sites at Smithfield and Billingsgate by a raft of existing UK local legislation, which imposes certain rights, restrictions and obligations as to the use of the land”.

The explanatory memorandum attached to the bill stated: “This bill provides for the repeal of legislation relating to Billingsgate Market and the London Central Markets, and the consequent cessation of the operation of those markets at the existing sites. The markets are owned and operated by the City of London Corporation.”

The bill received its first reading in the House of Commons on 22 January 2025.

Three groups/individuals submitted a “petition against the bill”. One, lodged by a Peter Acton, represented the “31,000 people who have signed the Save Smithfield Market petition on Change.org.” The “petition period” closed on 30 January.

The Norwich Livestock Market Act 2025 is a recent Private Bill to have received royal assent. This act relocated Norwich Livestock Market.

Hybrid Bills

A Hybrid Bill is a Public Bill, introduced by the government, that affects the general public but also has a particular and disproportionate impact on the private interests of specific individuals or organisations.

Hybrid Bills are very rare and are almost always used for major national infrastructure projects. Examples include the bills which led to the construction of the Channel Tunnel and Crossrail, and those that made provision for the HS2 rail.

In effect, the Hybrid Bill process is a means of securing parliamentary approval for major infrastructure projects. This takes the place of the usual planning process.

In theory, a Hybrid Bill could be a private members’ bill, but this is especially rare.

Hybrid Bills process

Hybrid bills are subjected to a “hybrid” process, combining elements usually reserved for public and private bills.

• The Commons Public Bill Office reviews all public bills before their first reading to determine whether they might be hybrid bills.
• An environmental statement must accompany the bill if it authorises the acquisition of land.
• If a bill appears to be hybrid and receives its first reading, it is then formally classified by officials appointed by the speaker of the House of Commons (the examiners of petitions for Private Bills).
• The bill then returns to the commons to receive its second reading on the principle of the proposed legislation (like a public bill).
• If the Hybrid Bill – having had its status confirmed by the examiners of petitions – passes its second reading, a “petitioning period” begins.
• A select committee is then formed to consider “mitigating the effects of the bill, and on any compensation or any adjustments that need to be made.” The committee, sitting in a quasi-judicial capacity, will hear objections from petitioners, who can give evidence directly to the committee. The petitions cannot challenge the principle of the bill, which has already been approved at second reading. The promoter of the bill, usually the secretary of state for the relevant government department, is an active participant in this process.
• At the end of the process, the committee reports the bill to the House, with or without amendments.
• The bill then normally undergoes a “normal” committee stage, before returning to the commons for its report stage and third reading (as a Public Bill would).
• The bill then goes through the same process in the House of Lords.

This protracted process, accounting for the typically localised impact of Hybrid Bills, means they will often spend a considerable amount of time making their way through parliament.

The original HS2 bill was introduced in November 2013. It only gained royal assent in February 2017.

The Holocaust Memorial Act, another Hybrid Bill, was introduced to parliament in February 2023. It was then carried over after the 2024 general election, before finally receiving royal assent in January 2026.

‘Hybrid’ controversy over the Aircraft and Shipbuilding Industries Bill

In May 1976, procedural squabbling over the exact nature of the government’s Aircraft and Shipbuilding Industries Bill sparked a bitter commons debate.

The speaker, following representations from Conservative MP Robin Maxwell-Hyslop, ruled that the proposed legislation was a ‘hybrid bill’ – meaning it would be subject to separate, more complex standing orders.

The government announced it would seek to sidestep the speaker’s ruling. It moved that “in view of the serious consequences to the industries concerned and for those employed in them of further delay and uncertainty… any [relevant] standing orders… are dispensed with.”

The debate on the motion was held on the evening of 27 May 1976. A division on a Conservative amendment to accept the speaker’s ruling was tied at 303 votes each. The speaker, George Thomas, used his casting vote to defeat the amendment – in line with ‘speaker Denison’s rule’, thus preserving the bill.

The government’s motion was then moved and agreed to by a single vote, 304 to 303.

This came, it was alleged, after a Labour MP broke his ‘pair’. A ‘paired’ MP is a parliamentarian that has voluntarily promised not to vote – in an agreement between government and opposition whips via the ‘usual channels’. The pairing enables another MP from a separate party to be absent, usually on account of illness, without impacting the outcome of a vote. Their effective abstention is cancelled out.

In the case of 27 May 1976, had the Labour MP not broken his ‘pairing’ agreement, convention would have compelled the speaker to defeat the motion with his casting vote. ‘Speaker Denison’s rule’ says the chair should not create a parliamentary majority where one does not exist.

Once the result was announced, a gleeful group of Welsh Labour MPs began to sing The Red Flag, a traditional socialist and party anthem.

With cries of “We’ll keep the red flag flying here” ringing round the chamber, an incensed Heseltine acted. In an apparently spontaneous act of fury, he marched to the table of the House, grabbed the 1.5-metre-long silver gilt Mace, and held it aloft, shouting at the Labour benches. James Prior, the shadow leader of the house, immediately intervened and wrested the Mace from him, returning it to its place.

Heseltine, in his capacity as shadow industry secretary, had led the debate for the Conservative opposition.

The Mace is the symbol of royal authority in parliament; without it, the House cannot lawfully sit or pass legislation. Removing it from its rightful place, as Heseltine did, is therefore considered a serious and singularly taboo act of disorder.

The speaker responded by suspending the sitting.

Heseltine, otherwise known as Tarzan for his famous mane of golden hair, issued an almost-immediate apology for his actions. “I was unwarrantably provoked by the singing of the Red Flag”, he said.

“I thought, ‘Here is a neo-Marxist group in the House of Commons. Having cheated over the motion, cheated in the lobbies, I thought that in the circumstances they might as well have the mace as well.’

“I rapidly realised this was a reflection on the authority of the speaker and the House. I tried to apologise and will do so unreservedly as soon as I can.”

Heseltine then delivered an official apology in a statement to the House of Commons on 28 May 1976. In a short statement, he said: “Last night, Mr. Speaker, I removed the Mace from its position. I deeply regret my action. I was hoping to be able to apologise to you and the House when you returned to the chair last night.

“That was not possible, and I now take this first opportunity of apologising unreservedly.”

Heseltine faced calls to resign from the shadow cabinet. He was subsequently shuffled, against his will, to the post of shadow environment secretary.

Meanwhile, the Conservative chief whip, Humphrey Atkins, issued a statement expressing his party’s fury over the government’s behaviour.

Atkins said: “The government won the second division by deliberately breaking a pair. It was a deliberate device by the government, and we are to end all pairing for the remainder of this session, including the prime minister.”

The Conservative opposition then boycotted all procedural cooperation with the government, including pairing, for the next month. This was a significant move, given the government did not have an overall majority. It risked the absences of MPs effectively dictating the outcome of votes.

On 22 June, Callaghan issued a statement saying the vote of 27 May would be “considered again”.

This motion relayed that “in the event of an equality of votes in a division on the motion in the name of Mrs Margaret Thatcher for the re-committal of the Aircraft and Shipbuilding Industries Bill to a select committee, Mr. Speaker shall declare that the question is agreed to.”

It was defeated by 320 votes to 293. As was the substantive motion relating to the bill’s alleged ‘hybridity’ (by 311 votes to 297).

The bill did not take on ‘hybrid status’, therefore. And yet, after all that, subsequent disagreement between the commons and Lords meant the bill ran out of parliamentary time and was ‘lost’.

The bill was reintroduced in the next session. Following concessions by the government, it received royal assent as the Aircraft and Shipbuilding Industries Act on 17 March 1977.

Additional resources

• House of Commons – Guidance on petitioning against a private bill: https://bills.parliament.uk/publications/57640/documents/5590
• Parliament.UK – Private bills currently before parliament: https://bills.parliament.uk/?SearchTerm=&Session=39&BillSortOrder=0&BillType=Category%3D1&BillStage=&CurrentHouse=&OriginatingHouse=&Expanded=False