Replacing a prime minister during a general election campaign

How could the Conservatives replace their leader?

Both the process for ousting a sitting Conservative leader and the process for electing a new one are dependent upon sitting Conservative MPs. Leaders face a leadership challenge if enough MPs write to the chair of the Conservative party 1922 backbench committee, with a new leader elected by Conservative MPs voting to choose two candidates to put to party members (if only one person is chosen by MPs there is no subsequent membership vote).  

However, as Parliament has been dissolved, there are no Conservative MPs and there is no 1922 committee. So it is unclear how a leader could be removed or how a new leader could be elected. If a sitting leader chose to resign, the party would have to establish a process. Again, it is not clear who would decide or oversee that process. In practice it would probably have to be developed by a combination of the previous 1922 executive committee, the cabinet and the chairman of the conservative party.  

If the prime minister resigned as party leader then would they also have to resign as prime minister?

The two roles are distinct, but the role of prime minister is now expected to be the leader of a political party. If a sitting prime minister stood down as party leader to allow a successor as leader to be chosen, they would normally stay on as prime minister until that process was concluded (as happened during the past four changes of prime minister under the Conservatives). They would then be expected to resign once a new leader was chosen. The key constitutional principles here are that there must be continuity of government and therefore a prime minister should not resign until a successor was clear, and that the prime minister must be someone who has constitutional legitimacy. The second principle is complicated when parliament is dissolved, because that legitimacy normally comes through being the person ‘most likely to be able to command confidence’ in the House of Commons.

Does a new prime minister also need to be the leader of the largest political party if parliament is dissolved?

In the same way that the incumbent prime minister remains prime minister throughout the election campaign, it is arguable that, even though parliament is dissolved, any replacement prime minister should also come from the Conservative party. But as there is no sitting House of Commons to test a potential leader’s ability to command confidence, this legitimacy could be called into question.  

What happens if a prime minister resigns without a clear successor?

The prime minister is considered the principal constitutional adviser to the Monarch and is expected to advise on a successor when they resign – though in practice it is usually obvious. This advice is not binding on the Monarch. They are also not expected to resign prematurely. In modern times there must be continuity of government. The country cannot be without a prime minister for an extended period of time.  

Can there be an acting prime minister during, and after, a general election campaign?

No such role exists constitutionally, but it would be possible to effectively appoint an interim prime minister while a process to choose a permanent PM took place. This is the process expected to occur if a prime minister resigned suddenly or died in office. But there is no automatic successor – the role of deputy prime minister is a title not a constitutional role.  

Can the King decide who should be prime minister?

A core constitutional principle is that the sovereign ‘should not be drawn into party politics’. If there is any doubt as to who should be prime minister it is for political parties to ‘seek to determine and communicate clearly to the sovereign who is best placed to be able to command the confidence of the House of Commons’. In the absence of the House of Commons, it would still be for the political parties to avoid a situation in which it is not clear who should be prime minister.  

Do other parties have to agree?

Given the absence of Parliament and the lack of a settled process within the Conservative party, replacing the leader of the party, or prime minister, during an election campaign is a potentially controversial and destabilizing act. The prime minister is the person upon which the functioning of government primarily rests, and therefore it is important that they carry sufficient legitimacy to be able to act with authority, particularly in the event of any crises or major event. For these reasons, anyone elected leader would likely need to have some constitutional legitimacy with other political parties. This means that other parties and particularly the official opposition would probably have to agree that the process for replacing the prime minister had sufficient legitimacy to result in someone who carried authority.  

Could a new prime minister cancel the general election?

There is no established legal mechanism to cancel the general election or restore Parliament. There are legal powers to postpone polling day in the event of the demise of the Crown. In the event of a major crisis it may be possible to use the civil contingencies act 2004 to find a legal route to change the election date, but the CCA defines such emergencies as a situation which threatens serious damage to human welfare, serious damage to the environment, or war, or terrorism. The appointment of a new prime minister would not meet those criteria.