British Prime Minister Keir Starmer's position is under serious threat after the Labour Party's heavy losses in local elections and calls from dozens of MPs for him to announce a timetable for his resignation or resign outright.
Despite the growing tension in power, a formal procedure to replace the leader has not yet been activated, write William James and Alex Richardson for "Reuters".
On Monday, several parliamentary secretaries and assistant ministers resigned, and more than 70 Labour MPs publicly called on Starmer to step down after his appeal for "one more chance" failed to calm the internal discontent.
According to British media, some of the influential ministers in the cabinet have also insisted that the prime minister present a plan for his resignation himself.
However, the internal rules of the Labour Party do not allow the leader to be removed only through declarations of dissatisfaction or a vote of no confidence by MPs.
The system requires organized support to unite around a specific candidate for a leadership battle.
So far, most of Starmer's critics have insisted that he voluntarily set a deadline for his resignation, instead of directly launching a procedure for his removal.
Former junior minister Catherine West has already made a formal attempt to test support for Starmer's removal, but this does not yet constitute a formal leadership challenge, and she herself has not announced her intention to run for the leadership post.
If Starmer refuses to resign, a possible contender must first must secure the support of 20% of Labour MPs in the House of Commons.
With the party's current 403 seats, this means a minimum of 81 MPs.
In addition, candidates must meet additional thresholds of support from local party structures and affiliated organisations, including trade unions.
If a leadership procedure is opened, Starmer will automatically be eligible to participate in the race if he decides to defend his post.
If only one candidate manages to meet the requirements, there will be no vote and he will automatically become party leader and prime minister.
If there is more than one candidate, the choice will be decided by a vote of Labour Party members and affiliated organisations.
The winner of this vote will take over the party leadership and the prime ministership.