When a government implements a manifesto pledge through legislation, the legal position is straightforward: the result is an Act of Parliament like any other. The harder question is whether its electoral pedigree should matter. Does the fact that a measure was put to, and endorsed by, the electorate give it any special weight? Courts have acknowledged manifesto commitments as part of the legislative context but have not treated them as binding. The House of Lords under the Salisbury-Addison Convention should not block the passage of a bill fulfilling a manifesto commitment. But there the special treatment ends.
This issue comes into focus where such legislation engages fundamental constitutional principles. A manifesto commitment to curtail judicial review, for example, would raise questions not of validity, but of constitutional probity. Should the existence of an electoral mandate shape how the legislation is interpreted, treated or scrutinised when rule of law concerns arise? The difficulty is that looking to the constitution offers no clear answer. It provides no settled account of the weight given to manifesto commitments in such situations, leaving their relationship with competing constitutional principles contestable and ultimately uncertain.
Salisbury-Addison
In the immediate aftermath of the 1945 general election, the Attlee government began to implement its programme of reform for a post-war UK. Then, Labour had a majority in the Commons, but the Conservatives had a majority in the Lords. The Conservative leader in the Lords, Viscount Cranborne (later Marquess of Salisbury), came to an understanding with Viscount Addison, Labour leader in the Lords, that it would be ‘constitutionally wrong’ for the Lords to ‘oppose proposals which have been definitely put before the electorate’. This restraint in the name of democracy came to be known as the Salisbury-Addison Convention. By that convention, the House of Lords as the unelected chamber should not block Bills which feature in the governing party’s most recent general election manifesto. A “Manifesto Bill” was recognised by the 2006 Joint Committee on Conventions as enjoying a ‘special form of democratic legitimacy as they have been voted for by the electorate’.
This special treatment of manifesto Bills has not gone unquestioned, though. The Wakeham Report on the future of the House of Lords, while primarily concerned with Lords reform, discusses the position and importance of manifestos in the context of the Salisbury-Addison Convention. The report that argued that giving additional constitutional protection to some Bills simply because they are truer to a manifesto commitment ‘would be unreasonable’ as (i) ‘it is rarely possible to interpret a general election result as evidence of clear public support for any specific policy’ as ‘only a tiny minority of the electorate ever reads party manifestos’ and (ii) ‘any given issue inevitably develops or changes over time’.
Although the Convention suggests a settled practice, its operation has from the beginning been marked by recurrent tensions, reform programmes, and manifesto commitments that have tested – and at times unsettled – the boundaries of both the Convention and wider constitutional norms.
Manifesto commitments and the constitution
Despite much radical content, in their 1945 election manifesto, the Labour Party did not ask for a mandate to abolish the House of Lords, or even to reform it. Instead, they promised they would not allow the House of Lords to ‘thwart the will of the people’, and when tensions arose between the Commons and Lords, the result was the Parliament Bill, which eventually became the Parliament Act 1949. It was designed to reduce the period of the Lords’ delaying power from two years to one and was initiated after conflict between the houses over the government’s Iron and Steel Bill. The passage of the 1949 Act, though, proved constitutionally controversial.
While the Bill had not featured in the party’s manifesto directly, it was justified on the basis that Labour’s reformist agenda had, in general, been mandated in the result of the 1945 election. Prime Minister Clement Attlee defended the Bill by framing it as ‘wise precautionary measure‘ to prevent the unelected upper chamber defeating legislation backed by the elected House of Commons. Consequently, it was argued that efforts by the Lords to block the 1949 Bill itself, and the more general pursuit of the party’s agenda was democratically illegitimate and against the will of the electorate. Ultimately, the 1911 Parliament Act had to be used to pass the Bill, and the 1949 Act, and the reduction in the Lords delaying power from two years to one, became law. The Parliament Act 1949 cemented the Commons’ primacy, underpinning the expectation that governments can ultimately enact manifesto commitments whatever opposition there might be in the Lords.
Two decades later, in 1970 the Conservative Party’s general election manifesto contained a commitment to secure entry in the European Economic Community (EEC). This was ultimately implemented through the European Communities Act 1972, giving effect in domestic law to rights and obligations arising under European Community law. As with other “manifesto Bills”, the government was able to rely on the policy’s inclusion in their manifesto as a source of democratic legitimacy in advancing the legislation.
However, the weight attached to that mandate was contested. While the manifesto supported EEC membership, it had not set out in full detail the constitutional implications of incorporating European law into the domestic legal order. Comments made in the course of parliamentary debate reflected this uncertainty, with the leader of the opposition Harold Wilson, describing the legislation as “an outrage against all the constitutional doctrines and practices of our democracy”.
Debate over EEC membership continued in the years that followed and the next Labour government held a referendum in 1975 on whether the UK should remain in the Community. Labour had included the referendum in their manifesto. Whether this was designed to attract votes or manage internal tensions within the party, the fact that it was included perhaps gave greater democratic legitimacy to a referendum held so soon after the UK had joined the EEC. That said, the very fact of the referendum itself is evidence that inclusion within a manifesto alone does not necessarily provide definitive constitutional authorisation for measures which create significant constitutional change.
Fast forward to 2015, and the Conservative Party manifesto included a pledge to reintroduce new communications data legislation, often referred to as the ‘snooper’s charter’, which had previously been blocked by their Liberal Democrat coalition partners. This manifesto pledge was eventually enacted in the form of the Investigatory Powers Act 2016, which consolidated and now governs surveillance powers used by various state bodies. Once enacted, it was subject to various legal challenges. Concerns with the Act included the limiting of judicial oversight, and the express empowering of the police and security services to hack and bug computers and phones. In one case brought by Liberty in 2022, the High Court ruled that it was unlawful for security services to obtain individuals’ communications data from telecom providers without having prior independent authorisation.
The Investigatory Powers Act 2016 was enacted in part due to the Salisbury-Addison convention. In this sense, the ‘Snoopers’ Charter’ and the legal challenges to it illustrate that an electoral mandate can justify constitutionally greylegislation, but not necessarily the unconstrained exercise of the powers it provides. While in various cases relating to the ‘Snoopers’ Charter’ the courts did not deny the weight of an electoral mandate, there remained an insistence that such legislation comply with the fundamental legal standards which are part of our constitutional framework, such as independent oversight and safeguards.
As such, we can recognise that the post-1945 settlement elevates electorally mandated Acts to a special status of sorts, capable of limiting institutional resistance. Yet this status cannot on its own insulate legislation from scrutiny, challenge or condemnation on grounds relating to constitutional principles which might include human rights or the rule of law more broadly. Together, these amount to a constitutional tension between majoritarian democratic legitimacy and our framework of legal constraints.
A hypothetical mandate to dismantle judicial review
To illustrate the uncertain constitutional weight of manifestos, consider a worked hypothetical. Suppose a political party wins a general election and forms a government on the basis of a manifesto which includes a commitment to dismantle a core component of the UK’s constitutional framework. For present purposes, let that commitment be the abolition – whether partial or complete – of judicial review.
At the political level, manifesto commitments carry recognised constitutional significance. Both the Salisbury-Addison Convention as well as broad appeals to parliamentary sovereignty are often framed in terms of democratic legitimacy deriving from a general election. In this sense, manifestos function as a conduit through which political authority is translated into legislative expectation.
Legally, however, manifesto commitments have no independent status. The fact that a policy appeared in a manifesto does not bind Parliament, nor does it alter the courts’ approach to statutory interpretation. At the most it may be said to lend democratic weight to the decision to legislate, but that weight operates in the political rather than the legal sphere.
One potential safeguard against constitutionally disruptive manifesto commitments lies in Parliament itself. Even with a House of Lords constrained by convention (and, if necessary, the Parliament Act), legislation must still secure the approval of a majority in the House of Commons. In theory, MPs could refuse to endorse a measure as constitutionally significant as the abolition of judicial review. In practice, however, the combination of party discipline, the whipping system and structural advantages afforded to the executive make such resistance unlikely, particularly where the measure in question formed part of the governing party’s electoral platform.
Once enacted, the orthodox position reasserts itself; under parliamentary sovereignty, courts do not strike down primary legislation. The question then becomes not whether such a statute would be valid, but how the courts would respond to it and whether such a policy being in a manifesto would be considered in their reasoning.
In Privacy International [2019] UKSC 22, the Supreme Court adopted a restrictive approach to an ouster clause, holding that even broadly framed provisions could not exclude judicial review of legal error absent the clearest wording. More broadly, the principle of legality has been used extensively to ensure that fundamental constitutional principles are not overridden by general or ambiguous statutory language.
Yet these doctrines are, in important respects, front-loaded. They operate to shape interpretation, not to resist clearly expressed legislative intent. If there was to be explicit and unambiguous statutory instruction to curtail or exclude judicial review, existing authority suggests that the courts are likely to give effect to that intention.
At this point, the manifesto mandate emerges as a potential, yet under-theorised factor. Where legislation clearly authorises incursions into fundamental constitutional principles, its legal validity is not an issue; the question is whether its electoral pedigree would add anything to the force of Parliament’s right to legislate in such terms. On one view, inclusion of the measure in the governing party’s manifesto may reinforce the democratic legitimacy of the statute and strengthen the case for judicial deference. On another view, the scale of the constitutional change – particularly one striking at the supervisory jurisdiction of the courts – may be thought to require more than the attenuated consent produced by a general election. The mandate, in other words, may be invoked as justification, or exposed as insufficient.
While decisions such as Privacy International 2019 demonstrate a clear judicial reluctance to accept the exclusion of review absent the most explicit statutory language, they stop short of suggesting that explicit statutory wording could be questioned. Obiter dicta comments such as in Jackson v Attorney General 2005 hint at the possibility of constitutional limits on Parliament in ‘exceptional circumstances‘, but without articulating how such circumstances are to be identified, or what role, if any, a prior electoral mandate would play in that assessment.
The result is a constitutional grey area. A manifesto commitment, translated into clear statutory form may well succeed in legal terms, yet its claim to constitutional legitimacy, particularly where it targets keystone aspects of the constitution such as judicial review, remains contestable. The weight accorded to such a mandate, whether as a shield against judicial scrutiny, a factor in its calibration, or ultimately as irrelevant, has not been definitively settled. In this respect, the constitutional status of manifesto pledges when brought into direct tension with the rule of law remains less a matter of doctrine than of unresolved constitutional judgement. When we look ahead to future elections, it’s imperative we establish more clearly what might be at stake if a party makes a manifesto commitment to enact policy of dubious constitutional legitimacy.
Ava Brass.
Ava Brass was an intern with the Constitution Society in 2026. She is a first year law student at Lincoln College, Oxford University.
The Constitution Society is committed to the promotion of informed debate and is politically impartial. Any views expressed in this article are the personal views of the author and not those of The Constitution Society.