Sir Keir Starmer is under immense pressure over his leadership of Labour after his party suffered devastating electoral losses across the country.
Growing numbers of the prime minister’s own MPs, including some former loyalists, have called for him to go.
Speculation over a leadership challenge had been growing for months before Thursday’s elections, with Andy Burnham, Angela Rayner and Wes Streeting all named as potential successors.
But on Saturday, it was a more obscure backbencher who issued an ultimatum for the cabinet to put an end to Sir Keir’s premiership.
Labour MP Catherine West told the cabinet that if they do not put someone forward to challenge Sir Keir by Monday, she will attempt to trigger a leadership contest herself.
The prime minister has insisted he will not quit, and cabinet minister Bridget Phillipson insisted on Sunday that Ms West was wrong as she continued to back Sir Keir.
But Ms West doubled down on her warning, saying she still intends to seek the backing of the 81 MPs needed to launch a challenge if the ultimatum is not met tomorrow.
Here is a look at how a potential Labour leadership contest could play out:
There is no formal confidence vote procedure to oust a Labour leader, which means challengers need to garner the support of the parliamentary party in order to oust them.
Any challenger would require the support 20 per cent of the party in the Commons, which is 81 MPs currently.
Ms West has pledged to launch a challenge with the backing of 10 MPs so far. This falls well short of the nominations required, but more would be likely to back her as a means to oust Sir Keir.
However, her move is intended to spur a potential leadership hopeful from the Cabinet into action.
Written nominations would need to be submitted to Labour general secretary Hollie Ridley, which would then trigger the contest.
In the case of a successful challenge, Sir Keir would be on the ballot by default as the incumbent and would not need to gather nominations. But if Sir Keir were to resign, it would automatically start a contest for a new leader.
It is up to the Labour Party’s National Executive Committee to set the timeline for a leadership election.
As talk has turned to the prime minister’s political future, some have drawn comparisons with Labour predecessor Sir Tony Blair’s exit from No 10 – but unlike then, when Gordon Brown was the clear candidate to replace him, there is no obvious successor to Sir Keir.
Speculation is rife around the ambitions of his former deputy Ms Rayner and Greater Manchester mayor Mr Burnham, but the former is still awaiting the outcome of a review into her tax affairs and the latter is not currently an MP.
