Jeremy Corbyn has faced a "hostile" meeting with Labour MPs and peers who told him he must quit for the sake of the party.
Many MPs appeared close to tears after a volatile meeting that fo rmer leadership contender Chuka Umunna described as "pretty catastrophic".
In extraordinary scenes former frontbencher John Woodcock and Mr Corbyn's press spokesman rowed in front of the huddle of journalists gathered in Parliament's committee corridor.
Despite the "overwhelming" criticism from across the parliamentary party, Mr Corbyn's aides insisted the Labour leader would not be quitting.
Mr Corbyn's authority has been left in tatters after two-thirds of his shadow cabinet quit in an open revolt against his leadership.
The Labour leader is likely to face a challenge for his position after losing 20 members from his top team and a raft of junior frontbenchers over the last 24 hours as months of frustration exploded into a full-blown rebellion.
Mr Corbyn was jeered as he used a Commons appearance to hit out at the rebels "indulging" in manoeuvres against him.
At a meeting of the Parliamentary Labour Party later the leader was told "for your sake but most importantly for the sake of the people who need a Labour government, do the decent thing".
MPs also called on him to "search inside yourself and ask if the electorate really think you are a prime minister in waiting", and he was told he "couldn't offer leadership".
Former Home Secretary Alan Johnson told Mr Corbyn he had taken his "share of responsibility, but you should take yours".
Chris Bryant, former shadow Commons leader, said: "The writing on the wall is eight metres high and if he can't see it he needs to go to Specsavers.
"The only person who can solve this for the Labour party and break the log jam is Jeremy himself.
"This is a battle for the soul of the Labour party."
Former communities minister Ian Austin said the "overwhelming majority of speakers were critical of Jeremy and saying he should stand down".
He added: "I have never seen a meeting like it but it's a big moment for the Labour party."
The Labour leader's official spokesman conceded that most of the speakers were "opposed to Jeremy's view or fairly hostile" during the meeting.
Mr Corbyn "has made it absolutely crystal clear already that he is not going to concede to a corridor coup or a backroom deal which tries to flush him out", he said.
"It's all about whispering in corridors, meeting together and people resigning from their appointed posts, but Jeremy Corbyn was overwhelmingly elected by the members of the Labour Party."
The leader will not "betray" the people who elected him, the spokesman added.
Seumas Milne director of strategy and communications, said: "There is one way if people want to change the leadership of the party, that is to stand a candidate, get the nominations and mount a challenge and have an election.
"Jeremy will be a candidate in that election. It's very straightforward."
As Mr Corbyn's aides finished briefing the press, a clearly angered Mr Woodcock attacked the team for revealing details of the "private" meeting.
Told by the Labour leader's official spokesman that he "slags us off to the media every day", the former shadow education minister said: "You are an unelected official standing outside briefing the media on what was supposed to be a private meeting that we held in there, giving a highly distorted account.
"When unelected people like this come out of the shadows and accuse Labour MPs who are deeply worried about the future of their country and the fact that t he Labour Party faces an existential threat from the leader that we have, to then be accused by Jeremy's unelected officials, who apparently never even attended a meeting of the Labour Remain campaign, is too much," Mr Woodcock added.
Mr Corbyn, meanwhile, headed to Parliament Square where he received a rapturous reception from supporters of the left-wing Momentum movement who rallied in a show of support.
The crowd cheered and waved placards reading "No Jexit" as Mr Corbyn told them: "We don't need a blame culture. We need a united culture."
The Labour leader made no direct reference to the challenges to his authority, but said: "Don't let the media divide us, don't let those people who wish us ill divide us. Stay together, strong and united, for the kind of world we want to live in."