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Why does the UK not have a "written" constitution?

Speaking to journalists in Sheffield in August 2026, the Prime Minister said his devolution agenda increased the case “for a written constitution”. There is, added Andy Burnham, “a case for a new clear set of principles about how this country should be run”.

This briefing examines the current status of the United Kingdom constitution and summarises the main arguments for and against a “written” or codified constitution.

The constitution of the United Kingdom

It is often said that the constitution of the United Kingdom of Great Britain and Northern Ireland is “unwritten”, or even that it does not exist. In fact, and as the Law Wales website notes, “most of the laws, conventions and understandings relating to the constitution are written down”, it is just that “they cannot be found conveniently written down all in one place”.

This lack of a “codified” constitution makes the UK unusual but not unique: Israel and New Zealand also lack fully written constitutions. However, and as the legal academic Nick Barber has observed, the differences between written and unwritten constitutions can be overstated:

large parts of the UK constitution are written, whilst large parts of the constitutions of states with a capital c Constitution lie outside of that document.

For example, the United States has a “capital c Constitution”, but its governance still relies on the “political construction of authoritative norms” or, as they are known in Westminster systems, “constitutional conventions”.

The academic JAG Griffith once argued that the UK constitution “is what happens […] if it works, it’s constitutional”. It was, he concluded, essentially a “political constitution” rather than a legal one. Christine Carpenter and Andrew Spencer have been more specific, defining a constitution as “the set of political, governmental and legal structures and shared values within which the business of everyday politics and governance operates”.

As the Supreme Court stated in its judgment on Miller II:

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.

The 2011 Cabinet Manual made a similar point, stating that there:

is no single document that describes, establishes or regulates the structures of the state and the way in which these relate to the people. Instead, the constitutional order has evolved over time and continues to do so. It consists of various institutions, statutes, judicial decisions, principles and practices that are commonly understood as ‘constitutional’

Why is the UK constitution unwritten?

In a 2007 article, the academics Vernon Bogdanor, Tarunabh Khaitan and Stefan Vogenauer identified two reasons why the UK lacks a codified constitution, one historical and the other conceptual. Explaining the historical reason, they wrote that unlike other countries, the UK had not had a “momentous development” that made a codified constitution necessary:

Most states promulgate constitutions following some momentous development, such as revolution, regime change, war or the attainment of independence. Such moments require the peoples concerned to reassure themselves of the shared values that form the basis of their society by giving themselves new rules for the future. That happened, for example, when the United States declared her independence from Britain in 1776, when India attained her independence in 1947, when France adopted new regimes in 1946 and 1958 and when Germany adopted a new regime in 1949. There is a ‘constitutional moment’ at which the rules by which a country is governed need to be clarified.

Conceptually, meanwhile, the UK constitution was not written because our:

dominant, perhaps our only, constitutional principle has been the sovereignty of Parliament. The 1689 Bill of Rights, unlike its American equivalent, did not entrench fundamental rights against a majority in the legislature. Instead, it guaranteed the rights of Parliament against the king. Instead of repudiating the doctrine of the sovereignty of Parliament, it emphasised it […] if Parliament is sovereign, the individual cannot have rights against Parliament. There was therefore no point in having a written constitution limiting the rights of Parliament. Indeed, the British constitution could have been summed up in just eight words – what the Queen in Parliament enacts is law.

Recent developments

There have been several independent or party-political attempts to codify the UK constitution:

• the Liberal Democrats in 1990
• the former Labour MP Tony Benn’s Commonwealth of Britain Bill in 1991
• the Institute for Public Policy Research (IPPR)’s The Constitution of the United Kingdom in 1991
• Professors Vernon Bogdanor and Stefan Vogenauer (and their students) in 2007
• Professor Robert Blackburn for a parliamentary committee in 2014

Gordon Brown, as Prime Minister (2007–10) and since, has expressed support for codification of the UK constitution. The 2007 Governance of Britain green paper referred to a “growing recognition” of the need to clarify “what it means to be the United Kingdom”, something that “might in time” lead to a written constitution. The green paper added that this could not “come into being except over an extended period of time, through extensive and wide consultation”.

In his 2022 Commission on the UK’s Future, Mr Brown said he and the other commissioners could see “the force” of arguments for “a wholly codified constitution to put constitutional limits on the power of government” but that it “would be a very major undertaking”.

In Head North, a 2024 book Andy Burnham co-authored with Steve Rotheram before becoming Prime Minister, Mr Burnham cited Mr Brown’s commission and said that he and Mr Rotheram recognised:

none of it will work unless we agree a new set of principles and rules for the running of the British state and the rights of its citizens; or, in other words, unless we build the new Britain on the strong foundation of a written constitution.

The 2024 Liberal Democrat manifesto included a commitment to support the “creation of a UK Constitutional Convention, with the aim of drafting a new Federal Constitution that sets out the powers of the government at each tier”.

The Scottish National Party also supports the creation of a written constitution for an independent Scotland which would put “democracy, rights and equality at the heart of everything we do as an independent country”.

Arguments for and against a written constitution

In its 2014 report, A new Magna Carta?, the House of Commons Political and Constitutional Reform Committee summarised “particular arguments” for and against the UK adopting a written or codified constitution. This was the last time a parliamentary committee examined this debate. Some of the arguments for a written constitution were:

• The UK’s so-called “unwritten constitution” exists only in the abstract. Matters of such fundamental importance should be codified into a single documentary constitution for all to see.
• Many basic rules about UK Government do not at present exist in any legal form at all but rely instead on unwritten understandings or traditions.
• The rules about our core institutions of government, especially the executive (ministers and civil servants), the legislature (the two Houses of Parliament) and judiciary, are fundamental and are of a different character from other kinds of law. They should be clearly distinguished from ordinary law and codified in a special document.
• Governing parties can too easily pass laws to change the country’s constitutional rules simply to benefit themselves. An entrenched written constitution would address this problem, setting down a minimum set of procedures that govern major constitutional changes.
• A written constitution would codify prerogative powers and make them subject to parliamentary or other controls, while replacing grey areas of constitutional conduct with clear legal provisions.

And some of the committee’s summarised arguments against a written UK constitution were that:

• The British system of government and its unwritten constitution works well in its present form and “if it ain’t broke, don’t fix it”.
• The United Kingdom has an evolutionary system of government that adapts smoothly to changing social and political conditions, whereas a written constitution entrenching its institutions and rules would be more rigid and difficult to change with a danger that it might fossilise and become out of date.
• A written constitution would politicise the judiciary, requiring the courts (and ultimately the Supreme Court) to form judgments on questions of a political nature that should more properly be dealt with by politicians through the normal parliamentary process.
• A written constitution would curb the ability of elected representatives and their officials to act quickly and flexibly to meet citizens’ needs.
• The preparation of a written constitution would involve a huge and disproportionate amount of time and effort […] There are far more pressing public policy issues for the government and Parliament to address, such as economic recovery and improving the quality of public services.

Critiques of the Prime Minister’s comments

In response to the Prime Minister’s call for a written constitution, Jonathan Sumption, a former Justice of the UK Supreme Court, wrote in the Telegraph newspaper that such a change would lead to two “important and undesirable” differences from the status quo:

The first is that any written constitution worthy of the name would serve as a code of supreme law, overriding all other sources of law. In other words, it would contain fundamental rules which could only be altered by a constitutional amendment under some special procedure such as a referendum or a super-majority in Parliament. This necessarily involves a certain rigidity […]

The second way in which a written constitution would make a difference is that by formalising the rules governing the operations of the state, it would hand enormous political powers to the courts. No written constitution can anticipate every problem that may arise. The most that it can be expected to do is to lay down general principles. The courts would necessarily have the power to interpret those principles, and to overturn acts of Parliament, however strong the democratic mandate for them, if they did not measure up to the courts' interpretations.

Lord Sumption also urged anyone who believed a written constitution to be “a necessary protection against the despotic state” to “look at the world around them”:

The US Constitution has not stopped power from falling into the hands of a coarse and divisive megalomaniac. The constitutions of South America have not prevented the usurpation of power by military dictators. Written constitutions did not save Germany from Hitler, or Italy from Mussolini, or France from Pétain.

Further reading

The United Kingdom constitution – a mapping exercise

Nick Barber, Against a Written Constitution, Public Law 11, 2013

Jeff King, The Democratic Case for a Written Constitution, Current Legal Problems 7:1, 2019