Constitutional Conventions in the UK Constitution
Constitutional conventions are non-legal rules that regulate the conduct of constitutional actors in the United Kingdom. They are not enforceable by courts but are regarded as politically binding by those to whom they apply. Conventions fill the gaps left by statute and common law, ensuring that constitutional practice conforms to democratic principles. The uncodified UK constitution relies particularly heavily on conventions to govern relationships between the Crown, Parliament, the judiciary, and the devolved institutions. Without conventions, much of the constitution would cease to function, as many fundamental constitutional arrangements—including the appointment of the Prime Minister, the exercise of prerogative powers, and the relationship between the Houses of Parliament—are governed entirely by conventional rules.
Defining Conventions
Conventions are rules of political practice regarded as binding by constitutional actors but not enforced by courts. A V Dicey distinguished conventions from laws by enforcement: laws are enforced by courts, while conventions are enforced by political sanctions including loss of confidence and ministerial resignation. Sir Ivor Jennings identified three criteria for a convention: precedents showing the practice; actors believe they are bound; and a constitutional reason for the rule. This test was approved in R (Miller) v Secretary of State for Exiting the European Union (2017). Conventions differ from mere practices in being regarded as obligatory, with breach carrying political consequences even though no legal sanction attaches.
The Sewel Convention
The Sewel convention (also known as the legislative consent convention) provides that the UK Parliament will not normally legislate with respect to devolved matters without the consent of the relevant devolved legislature. The convention is named after Lord Sewel, who announced it during the passage of the Scotland Act 1998. The convention was given statutory recognition in section 28(8) of the Scotland Act 2016 and equivalent provisions for Wales, providing that the UK Parliament “will not normally” legislate on devolved matters without consent. In R (Miller) v Secretary of State for Exiting the European Union (2017), the Supreme Court held that the Sewel convention is a constitutional principle that is cognisable by the courts but is not legally enforceable. The Court stated that the policing of conventions belongs to the political realm and that the legal enforcement of conventions would be inconsistent with their character as non-legal rules. The convention has been tested in the context of Brexit, with the UK government proceeding with the European Union (Withdrawal) Act 2018 despite the refusal of the Scottish Parliament and the Senedd to grant legislative consent. This has prompted debate about whether the convention retains its force when breached.
The Salisbury-Addison Convention
The Salisbury-Addison convention provides that the House of Lords will not oppose government bills that implement manifesto commitments. Formulated in 1945, it reflects the principle that an unelected second chamber should not frustrate the programme of an elected government. The convention now applies to the government’s legislative programme generally, though the Lords retain power to amend and scrutinise. It is supported by the Parliament Acts 1911 and 1949, which provide a mechanism for overriding the Lords’ veto. The convention has faced strain in recent years, with the Lords occasionally defeating government bills.
Collective Cabinet Responsibility
The convention of collective Cabinet responsibility requires that all ministers support government policy in public or resign from the government. The convention has two aspects: first, that government decisions are binding on all ministers; second, that ministerial disagreements about policy are kept confidential. The convention ensures that the government presents a united front to Parliament and the public, and that Cabinet decisions are taken collectively. The convention was considered in Attorney General v Jonathan Cape Ltd (1976), where the court recognised the convention but declined to enforce it as a legal obligation. The publication of the Crossman Diaries prompted debate about the confidentiality of Cabinet proceedings and led to the development of a qualified duty of confidentiality for Cabinet documents. The convention has been modified in practice: the Prime Minister may authorise collective agreement to differ in coalition governments, allowing ministers from different parties to express differing views on specific issues. The coalition government of 2010-2015 operated such arrangements, allowing Liberal Democrat and Conservative ministers to maintain differing positions on certain European Union matters while remaining in government.
Individual Ministerial Responsibility
Individual ministerial responsibility requires ministers to account to Parliament for their own conduct and for their departments. Ministers must give accurate information to Parliament and resign in cases of serious misconduct or departmental failure. The convention has evolved: until the mid-twentieth century, ministers routinely resigned following departmental failures (as with Sir Thomas Dugdale over the Crichel Down affair in 1954). In modern practice, a distinction has developed between political responsibility (for which ministers remain answerable) and operational responsibility (for which civil servants may account directly to select committees). The Ministerial Code sets out standards of conduct, though breaches do not give rise to legal consequences.
Jennings’ Test and Identifying Conventions
The three-part test formulated by Sir Ivor Jennings provides the principal method for identifying constitutional conventions. The first question is whether there are precedents for the practice. Second, whether the actors concerned believe they are bound by the rule. Third, whether there is a constitutional reason for the rule. The test was applied by the Supreme Court in Miller (No 1) (2017), where the Court examined the Sewel convention and concluded that while it satisfied Jennings’ test, it remained a non-legal rule not enforceable by courts. The test has been criticised for being imprecise and for relying on the subjective beliefs of political actors. It has also been noted that conventions can arise quickly without extensive precedent, and that the third element of the test (constitutional reason) may be difficult to apply objectively. Nevertheless, Jennings’ test remains the standard approach for identifying conventions and has been applied by courts, parliamentary committees, and academic commentators.
Codification and the Cabinet Manual
Several conventions have been codified. The Cabinet Manual (2011) provides a written guide to the laws and conventions governing government, covering the appointment of the Prime Minister, Cabinet operation, and dissolution. It has no legal force but provides authoritative guidance. The Fixed-term Parliaments Act 2011 codified the dissolution convention, though the experience showed codification can create unforeseen problems; the Dissolution and Calling of Parliament Act 2022 reversed it, restoring the prerogative while retaining some statutory elements. Codification raises questions about whether conventions lose their character when reduced to writing: some argue it transforms political obligations into legal ones, while others contend conventions can be codified without losing their essential character.
Legal Recognition: Miller and Cherry
The Supreme Court in R (Miller) v Secretary of State for Exiting the European Union (2017) recognised the Sewel convention as an important constitutional principle but declined to enforce it, holding that legal regulation would be inconsistent with its character. In R (Miller) v The Prime Minister (2019) (the Cherry/Miller case), the Court held that the prerogative power to prorogue Parliament was limited by the principles of parliamentary sovereignty and parliamentary accountability. The Court did not enforce a convention but identified constitutional limits on prerogative power that give legal effect to the principles underlying conventions. These cases established that conventions, while not legally enforceable, are constitutionally significant and may influence the interpretation of statutes and the scope of prerogative powers.