The constitution

A constitution is the set of rules that establishes the institutions of the state, sets out their powers and defines the relationship between the state and its citizens.

The UK constitution has three defining features. It is uncodified: there is no single document with higher legal status than other law. It is unentrenched: constitutional laws can be changed by an ordinary Act of Parliament passed by a simple majority, with no special procedure. And it is unitary: sovereignty lies with Parliament at Westminster, and the powers of the devolved bodies were granted by Acts of Parliament.

Two principles are often called its twin pillars. Parliamentary sovereignty means that Parliament can make or unmake any law, and that no Parliament can bind its successors. The rule of law means that everyone, including the government, is subject to the law, and that the law applies equally. A. V. Dicey identified both as core principles of the constitution in his Introduction to the Study of the Law of the Constitution (1885).^[3]

The five main sources. Because the constitution is uncodified, its rules have to be found in several places.

Statute law means Acts of Parliament, such as the Human Rights Act 1998 or the Scotland Act 1998. It is the highest source, because under parliamentary sovereignty an Act overrides every other source of law.^[9]

Common law is law developed by judges through precedent. It includes long-standing liberties and principles, such as the courts’ power to decide the legal limits of the government’s prerogative powers.

Conventions are unwritten rules that are followed because they are accepted, not because a court will enforce them. Examples include the monarch granting Royal Assent to bills passed by Parliament, and the Sewel Convention that Westminster will not normally legislate on devolved matters without the consent of the devolved legislature.

Authoritative works are books by constitutional experts that are treated as guides to how the system works, such as Dicey’s Introduction to the Study of the Law of the Constitution, Walter Bagehot’s The English Constitution and Erskine May’s guide to parliamentary practice. They have no legal force of their own.^[3]

Treaties are agreements with other states that shape UK law and government. The European Convention on Human Rights, given effect in UK law by the Human Rights Act, is the main current example. EU membership was the largest treaty-based influence on the constitution until the UK left the EU. The European Union (Withdrawal) Act 2018 kept most EU-derived law in force as “retained EU law”, renamed “assimilated law” from 1 January 2024.^[10][11]

The Labour governments elected in 1997 carried out an unusually wide programme of constitutional reform. Most of the changes dispersed power away from Westminster or placed new legal limits on government.

Supporters argue that these reforms brought government closer to the people, protected rights in law and separated the senior judiciary from the legislature. Critics argue that they were piecemeal: the Lords remained unelected, the Commons voting system was unchanged, and the position of England within a devolved UK was left unresolved.

Governments since 2010 have continued to change the constitution, but in smaller and less connected steps. The specification groups the main changes under four headings: the House of Lords, devolution, electoral reform and human rights.

Change since 2010 has been incremental and sometimes reversed. The Fixed-term Parliaments Act lasted just over a decade, and English votes for English laws, introduced in the Commons in 2015, was abolished in 2021. Defenders of the uncodified constitution see this as healthy flexibility. Critics see a constitution that can be reshaped at the convenience of the government of the day.^[37]

Devolution transfers power from Westminster to institutions in the nations and regions, while Parliament remains sovereign. It is asymmetric: each nation has a different settlement, and England has no parliament of its own.

Scotland. The Scottish Parliament has 129 members (MSPs), 73 for constituencies and 56 for regions, elected by the Additional Member System. It can make primary law on any matter not reserved to Westminster, including health, education, justice and local government. Reserved matters include defence, foreign affairs, immigration and the constitution. Since the Scotland Act 2016 it has also set income tax rates and bands on earnings and other non-savings income. The Scottish Government, led by the First Minister, is accountable to the Parliament.^[38][17][27]

Wales. The National Assembly for Wales began with limited powers. It gained limited law-making powers in 2007, and after a referendum in 2011, in which 63.5% voted Yes, it gained full powers to pass Acts in all devolved areas, and the Wales Act 2017 moved Wales to a reserved powers model similar to Scotland’s. Renamed the Senedd in 2020, it was enlarged to 96 members for the 2026 election, elected by the Closed Proportional List System. The Welsh Government is led by the First Minister.^{[39][28][40][41]}

Northern Ireland. The Northern Ireland Assembly has 90 members (MLAs), elected by the Single Transferable Vote, and was created under the Good Friday Agreement of 1998. The Assembly had 108 members until 2017. Its Executive is based on power-sharing: since 2007 the First Minister has been nominated by the largest party in the Assembly, and the deputy First Minister by the largest party of the largest other designation (unionist or nationalist). The two offices have equal powers. The institutions have not functioned for long periods, most recently from February 2022 until February 2024.^[42][43][44]

England. London has had an elected Mayor and London Assembly since 2000, and many English areas now have combined authorities led by directly elected mayors. A proposed elected regional assembly for the North East was rejected in a 2004 referendum, by 77.9% to 22.1%. The English Devolution and Community Empowerment Act 2026 is the latest attempt to extend devolution within England. There is no English parliament: laws for England are made by the UK Parliament, where MPs from all four nations vote.^{[18][45][46][35][36]}

The impact of devolution. Supporters argue that devolution has brought decisions closer to the people affected by them, allowed policy to differ to suit each nation, and supported peace in Northern Ireland. Critics argue that it has strengthened demands for independence, created the “West Lothian question” (MPs from Scotland, Wales and Northern Ireland voting on laws that apply only to England), and left England without a voice of its own.

Devolution has not changed the legal basis of the constitution. In 2022 the Supreme Court ruled that the Scottish Parliament cannot legislate for an independence referendum without Westminster’s consent, because the Union is a reserved matter. See Current affairs below.^[49]

Debate about the future of the constitution centres on three questions. Should the reforms made since 1997 go further? How far should devolution in England be extended? And should the constitution be codified and entrenched, including a bill of rights?

Further reform of the Lords. Hereditary peers no longer sit in the Lords after 2026, but the chamber remains wholly unelected. Options include an elected or partly elected chamber, a smaller appointed chamber with a retirement age, or abolition.^[34]

Devolution in England. Options include an English parliament, elected regional assemblies, stronger combined authorities with metro mayors, or a return to English votes for English laws in the Commons.

A bill of rights. Some argue for a UK bill of rights entrenched above ordinary law. Others want to replace the Human Rights Act with a British bill of rights that would reduce the influence of the European Court of Human Rights. The Bill of Rights Bill introduced in 2022 was withdrawn in 2023.^[31]