The UK constitution contains numerous ways that a serving Prime Minister can be deposed. Although we’ve seen this happen frequently in recent history—and especially over the past year—a wider discussion about these various exit points and their significance for the UK constitution has yet to emerge. But these exit avenues are undoubtedly important. Many world leaders have consolidated power in various ways in recent years, and some have floated refusing to leave office or staunchly resisted doing so. UK constitutional actors can and should be aware of these threats, and take measures to prevent them from happening. This post identifies four mechanisms for how UK leaders may be ousted: two formal options and two less formal options. It then further reflects on these mechanisms in terms of operation and recent events. At a time when many people lament the upholding of norms and values in the UK constitution, analysing these mechanisms could prove useful when assessing the need for and potential prospects of reform. 

One quick caveat: general elections can of course bring about a change of government, and therefore a change of leadership. This blog post is predominantly focused on exit points outside of regularly timed general elections, as it’s these that have played such a prominent role in recent years. 

Exit Point #1: Confidence Votes

At any moment a government can fall if a motion of confidence in the House of Commons goes against it. If this happens a general election can be held or an alternative government could attempt to gain parliamentary confidence. Either way, a new government will come into power. This is the feature of the UK constitution that Tomkins called ‘simple’ and ‘beautiful’ (p 1). It means that any government (majority, minority, or coalition), must keep the confidence of the Commons. Keeping this confidence ultimately means that governments must keep their backbenchers happy—including, at times, those of their minority government or coalition partners. If they don’t, then they may not be in power for long. 

Confidence votes have a dualistic quality to them, as they can also be used by the government to pass controversial legislation and manage backbenchers. Indeed, the threat of triggering a possible general election may be reason enough for backbenchers to fall in line (p 269), although this strategy is still considered ‘high risk’. 

Confidence motions occur in a variety of settings, but the key point from Erskine May’s guidance is that the Commons must know it’s voting on the immediate fate of the government. For a while these votes were somewhat formalised by the Fixed-term Parliaments Act 2011, where certain procedures had to be followed. The Dissolution and Calling of Parliament Act 2022 repealed these procedures. 

Confidence motions remain the highest-level constitutional mechanism to bring down a government, but they are exceedingly rare. Although relatively common throughout the 19th century, only four governments since 1895 have lost a confidence motion (p 23), making it an unlikely—but certainly not an unheard of—way for a leader to exit. 

Exit Point #2: Party Challenge/Replacement

Party leadership challenges are less formal mechanisms than confidence votes, but are still formalised according to party procedures. This mechanism is also less direct than confidence votes, as a party leader may resign or be deposed and still remain prime minister, as Boris Johnson did until a new party leader was elected. 

The UK constitution is famous for its lack of entrenchment and, at least before the FTPA 2011, its lack of significant voting thresholds—one exception was the FTPA, which required ⅔ of sitting MPs to vote in favour of triggering an early general election, but this requirement has now been scrapped. This was an unusual clause, as Westminster generally operates through bare majorities. But when it comes to party leadership challenges, thresholds matter. For the Conservative Party, the significant threshold is 15% of MPs; for Labour it’s 20% of MPs. 

If 15% of Conservative MPs write to the Chair of the 1922 Committee then a leadership vote can be held. Essentially this amounts to a party confidence vote in the current leader and can happen whether or not the party is in government or in opposition. If MPs vote to oust the current leader, then a formal leadership election is held. 

For Labour, if one wants to mount a leadership challenge 20% of sitting MPs must write to the general secretary of the party that they support the challenger. If this threshold is reached, a leadership election is triggered. The current leader is automatically on the ballot and does not need to seek nominations.  

But neither of these party mechanisms have produced much change in terms of leadership, especially in recent years. Threats to write letters may prove politically useful at times in terms of warning leaders, but beyond that leaders are not frequently removed under formal challenges. Jeremy Corbyn survived a challenge to his leadership in 2016. Theresa May and Boris Johnson survived similar challenges to their leadership. 

Changing party leader when a government is in power is not uncommon, but it’s not usually leadership challenges that bring down prime ministers. More frequently, these challenges serve as warnings to leaders that their position may soon be untenable. 

Exit Points #3 & #4: Resignation – Wilful (3) and Forced (4) 

The most common exit point for a serving Prime Minister is resignation. Generally, these come in wilful and forced scenarios, although at times it may be difficult to tell which category a resignation belongs to. 

Exit Point #3: Wilful resignation occurs when a prime minister leaves office on their own volition (or perhaps with a gentle nudge). Such events most commonly occur immediately after the electorate has given its view at the ballot box. The most prominent recent example is David Cameron’s resignation after the 2016 Brexit referendum. There was no constitutional need for him to resign, but given that he campaigned on the side of Remain, he thought it appropriate. Perhaps Tony Blair’s 2008 resignation to make room for Gordon Brown also fits in this category. There was no constitutional or overwhelming political reason for him to step aside, but he did so.  

Exit Point #4: Forced resignation occurs when the leader of a political party is pressured into quitting by colleagues and others, and the decision to step down is ultimately taken out of the leader’s hands. 

The past three Conservative Prime Ministers have fallen victim to forced resignation: Theresa May, Boris Johnson, and Liz Truss. Two of them, Theresa May and Boris Johnson, survived confidence votes in their government and also Conservative Party challenges to their leadership And yet, they both ultimately succumbed to resignation. Liz Truss’s government didn’t have much time for either of these mechanisms to take shape, and she resigned after 45 days in office, becoming the shortest-serving Prime Minister in the history of the UK. 

Boris Johnson’s downfall is the most intriguing, because from a constitutional perspective he was undoubtedly safe when he was ousted. Johnson had won the Conservative Party confidence vote 211-148 on 7 June 2022. Under Party rules, nobody could challenge his leadership until 12 months after that leadership challenge (of course, the rules could have potentially been changed regarding when the next vote could take place, but that is purely hypothetical). And the Conservatives held a healthy parliamentary majority, so it was unlikely that a confidence vote was going to bring the government down. 

But from a less-formal constitutional perspective, he definitely wasn’t safe. He was vulnerable because of the recent leadership and parliamentary challenges, and also because of other things: the Partygate investigation, the cost of living crisis, and the Owen Patterson row, to name a few. His appointment of Chris Pincher, who had been accused of sexual assault, as Deputy Chief Whip ultimately led to his downfall. This set of events culminated in the largest number of ministerial resignations in modern history, with most happening in a very short space of time.

Forced resignation differs from exit points #1 and #2 through its informality. It’s not articulated in any comprehensible way; it merely ‘happens’. This means that there are no explicit standards or guidelines to go by, and that it may lead to leaders believing they were ‘forced’ out. Nevertheless, it aligns with exit points #1 and #2 in the sense that the decision is taken out of the leader’s hands. Someone, or perhaps a group of people, has told the leader that their time is up.  

Reflecting on the exit points

Ultimately, the UK constitution contains four methods by which leaders can be deposed without their consent: confidence votes, leadership challenges, forced resignation, and regularly timed general elections. It also allows for leaders to admit that their time is up and willingly resign. In all, this means that there are five potential leadership exit points within the UK constitution, and probably also within many parliamentary systems around the world. 

That informal rather than formal mechanisms have recently impacted politics so significantly says something about the UK constitution, although it’s difficult to pin down exactly what. Perhaps it shows the resilience of the political constitution. Perhaps it displays the constitution’s unique capacity for nimbleness and action, as opposed to the slothfulness and inaction seen in other political systems. And further, it may even show the capacity of the constitution to quickly respond to other factors, such as economic emergencies, intense media backlash, or a potentially dangerous or incompetent leader. But to some observers, recent events may also demonstrate a lack of structure and principle for some of the most important UK institutions. Others may consider it a recipe for instability, or even a flawed continuation of the ‘good chaps’ theory of government (on which see the discussion here following Q5). 

There’s wide consensus that Boris Johnson was the most significant threat to the UK constitution in a long while. And yet the constitution—one way or another—found a way to oust him. He may well work his way back into No 10. But if he does, like any other future prime minister, he’ll be subject to not just the formal constitutional mechanisms mentioned above, but also the informal, and potentially more dynamic, leadership mechanisms that all leaders in the UK must face.

The problem for both constitutional reformists and constitutional defenders is that the system has worked relatively well, even amongst the turbulence of the past few years, but we don’t have a clear explanation as to why. There’s no constitutional provision, standard, or decision that proved decisive. That may be less a downside than it is a normal—even a potentially desirable—feature of politics, and especially parliamentary politics. As Bernard Crick said, ‘diverse groups hold together, firstly, because they have a common interest in sheer survival and, secondly, because they practice politics—not because they agree about “fundamentals”, or some such concept too vague, too personal, or too divine ever to do the job of politics for it’ (2nd ed, p 24). The UK constitution does have one fundamental rule when assessing leaders—the need for confidence—and this rule operates on multiple levels and has different constituencies (e.g., MPs, ministers, party, electorate). But it’s a practical standard that encourages politics, rather than vague or divine concepts, to resolve these tensions. And although it may ultimately happen much later or much earlier than many people would like, this mix of formal and informal mechanisms when deposing UK prime ministers remains effective. 

Many thanks to Alison Young, Richard Kirkham, Mike Gordon, and Se-shauna Wheatle for comments on a previous version of this piece. 

Brian Christopher Jones is a Lecturer in Law at the University of Sheffield.

(Suggested citation: B.C. Jones, ‘Leadership exit points in the UK constitution’, U.K. Const. L. Blog (5th June 2023) (available at https://ukconstitutionallaw.org/))