The starting gun on Keir Starmer's long-awaited leadership challenge was fired tonight by a former minister.
Catherine West, a backbencher, revealed she will go public with a leadership coup on Monday if the Cabinet hasn't moved against the Prime Minister by her deadline.
The MP for Hornsey in north London went public with her announcement in an interview with the BBC this evening, in a move that may force key players like Angela Rayner and Wes Streeting to act.
Ms West said she already has 10 people prepared to back her, but this is well short of the 81 required to start a leadership election.
The former Foreign Office minister said: 'This afternoon I would like the Cabinet to come around the table and elect a leader amongst themselves, without humiliating the current leader Keir Starmer…
'But we need someone from within the current Cabinet to step forward as the leader and then we will have a new leader of the party without having to have a leadership election.
'If that cannot happen, and there are no leadership hopefuls that come forward tomorrow, then Monday morning I will put my name forward to stand for the leader of the Labour Party.'
She demanded that a prominent Cabinet minister emerge as the appointed successor to Sir Keir, 'who can really sell Labour values and sell our programme'.
Catherine West demanded that the Cabinet announce a candidate to replace Keir Starmer by Monday
Nearly 40 MPs have now gone public demanding that Keir Starmer bring his time in No. 10 to an end
Ms West did not specify whom she believes to be the best candidate.
She argued: 'I don't have a candidate. That's part of the problem.'
'But I think there are several people who would like to do it, who have been planning for months, but I'm very surprised that none of them has popped up today to say 'I will do it'.'
While the announcement set Westminster into overdrive, allies of the Prime Minister insisted that Ms West would not succeed in removing him next week.
One dismissed former Islington council leader Ms West as a 'misguided North London MP'.
He also told the Mail that her intervention was 'probably a good thing' for the PM as it would 'lance the boil' of speculation over a potential stalking horse challenge against Sir Keir, with rebels now forced to either back Ms West or back off.
Another Labour source privately mocked Ms West's challenge, saying she was 'best friends with Jeremy Corbyn'.
Downing Street appears to believe that Ms West is acting alone, and not as a stalking horse on behalf of any actual contender for the crown.
Her bombshell intervention came after a day of yet more Labour MPs publicly calling on Keir Starmer to start organising his departure from Downing Street.
The current number publicly saying he should either quit immediately, or set out a timetable, has risen to 37.
Ms West made her fury about the current leadership known this morning, when she also called on Sir Keir to resign.
She was followed by Debbie Abrahams, the MP for Oldham East, told the Today Programme she thinks 'it is a matter of months' before Starmer will have to decide whether to resign if he doesn't immediately turn things around.
Clive Betts (MP for Sheffield South East) agreed: 'There is a responsibility on the Cabinet to recognise this can't carry on forever.'
Wes Streeting reportedly has the 81 MPs required, but does not want to announce his candidacy first
Angela Rayner is also mulling a bid for leader
But Keir Starmer ally Lucy Powell, the Labour deputy leader, condemned her colleagues' plotting and warned that a leadership coup would make the party look 'ludicrous'.
Speaking on the BBC this morning, Ms Powell said Labour needs to change its approach, but with Keir Starmer at the helm.
She argued that Sir Keir 'is accepting responsibility, he is saying we've got to change. He hears what people are saying'.
The Manchester MP said that the Prime Minister is 'very reflective' on yesterday's brutal verdict by voters.
But she lashed out at Labour MPs demanding a change of leadership, arguing: 'I don't want to hear about that anymore. I want us to get on with the job.'
Asked whether Sir Keir will still be the party's leader in six months' time, she emphatically replied: 'Yes, yes, yes!'
Labour MPs who have called for Keir Starmer to resign, or set out a timetable for a leadership contest
Debbie Abrahams (Oldham East and Saddleworth) - 'I think it¿s a matter of months.'
David Baines (St Helens North) - 'When you¿re the leader, the buck stops with you.'
Paula Barker (Liverpool Wavertree) - 'Need to agree a clear timetable for change.'
Apsana Begum (Poplar and Limehouse) - 'There needs to be a superspeed change, in both leadership and policy.'
Clive Betts (Sheffield South East) - 'I don't think rebooting and refreshing is going to make any difference.'
Olivia Blake (Sheffield Hallam) - '[Starmer] needs to think about his position.'
Jonathan Brash (Hartlepool) - '[Starmer should] set out a timetable for his departure.'
Richard Burgon (Leeds East) - 'The party should now work towards a timetable for an orderly transition to a new leader.'
Ian Byrne (Liverpool West Derby) - 'PM must now set out a clear timetable for his departure.'
Beccy Cooper (Worthing West) - Shared Louise Haigh's call for a timetable.
Neil Duncan-Jordan (Poole) - 'All those responsible must seriously consider their positions.'
Barry Gardiner (Brent West) - 'He should stand aside.'
Louise Haigh (Sheffield Heeley) - 'The Prime Minister cannot lead us into another election.'
Chris Hinchliff (North East Hertfordshire) - 'I'm afraid I do now believe the Prime Minister should resign.'
Terry Jermy (South West Norfolk) - 'Keir Starmer, as leader of our party, needs to consider whether he is the right person to take the party and the government forward.'
Kim Johnson (Liverpool Riverside) - 'I personally don't think Keir will be leading us into the next election.'
Ruth Jones (Newport West and Islwyn) - 'He needs to be a bit more reticent about what he's saying about carrying on forever.'
Peter Lamb (Crawley) - 'He should set out a timetable for his departure.'
Ian Lavery (Blyth and Ashington) - 'Keir Hardie started the Labour Party¿ It could be another Keir ¿ Keir Starmer ¿ that could end the party forever.'
Brian Leishman (Alloa and Grangemouth) - 'Keir Starmer¿s position is untenable.'
Emma Lewell (South Shields) - Asked if it's time for the PM to go, replied: 'It's looking like it. Because once you've lost the trust of the British public it's very hard to get that back.'
Clive Lewis (Norwich South) - 'A timetable for his departure is now necessary.'
Justin Madders (Ellesmere Port) - 'Changing the person at the top is no guarantee that we can persuade the public we do have answers, but there will come a point soon when, without fundamental change, it will become necessary to do that'
Rachael Maskell (York Central) - 'It is inevitable that the PM is going to have to step down.'
Andy McDonald (Middlesborough and Thornaby East) - 'We need a change of leader tied to change of policy.'
John McDonnell (Hayes and Harlington) - '[PM] will need to put party first and country first in judging whether he is risking opening the door to Farage.'
Anneliese Midgley (Knowsley) - 'It's clear the PM can't lead us into another election.'
Abtisam Mohamed (Sheffield Central) - 'The PM should now agree a clear transition and timeline for new leadership.'
Connor Naismith (Crewe and Nantwich) - 'It is clear to me that we need new leadership.'
Simon Opher (Stroud) - 'We need an orderly transition.'
Kate Osborne (Jarrow and Gateshead East) - 'He can't lead us into another general election.'
Sarah Owen (Luton North) - 'Keir needs to resign.'
Euan Stainbank (Falkirk) - 'It is time for the Prime Minister to resign to allow for new leadership of the country.'
Graham Stringer (Blackley and Middleton South) - 'I don't think he can fight the next election if the Labour Party wants to survive.'
Jon Trickett (Normanton and Hemsworth) - 'The message from my constituency is that it's curtains for Keir.'
Tony Vaughan KC (Folkestone and Hythe) - 'We must give the public a Labour leader with a clear vision.'
Nadia Whittome (Nottingham East) - 'I believe the Prime Minister should announce a timetable for his departure.'
Interviewed this afternoon, Starmer said the local election results had been 'really tough' and he would 'reflect and respond' to the message delivered by voters.
'I'm not going to walk away and plunge the country into chaos, I think the right thing to do is to rebuild and show the path forward.
'We made a number of really important calls in the last couple of years... we need to couple to that the arguments we're making about hope and the future.
'I will be setting out those arguments... setting out with clarity the values and convictions that drive me.'
Asked if he would stand for the leadership if challenged, he notably swerved the question.