Theresa May faced shouts of "resign" as she endured another bruising Commons appearance over Brexit.
Opposition MPs heckled the Prime Minister and urged her to step down after she confirmed a delay to the vote on her Brexit deal.
Tory MP Andrew Bridgen (North West Leicestershire) also claimed she has "lost the trust and credibility" of the Commons, the country and the EU.
Labour leader Jeremy Corbyn warned an "extremely serious and unprecedented situation" had emerged, adding: "The Government has lost control of events and is in complete disarray."
He also said: "The Prime Minister is trying to buy herself one last chance to save this deal.
"If she doesn't take on board the fundamental changes required then she must make way for those who can."
After Mr Corbyn further criticised Mrs May for her handling of the Brexit process, Liberal Democrat leader Sir Vince Cable further put the boot in before appealing to the Opposition leader to act.
Sir Vince said: "With the fiasco today, the Government has really lost all authority.
"Let me just say that I and my colleagues will fully support the Leader of the Opposition (Mr Corbyn) if he now proceeds to a no confidence vote, as duty surely calls."
With the Irish border backstop causing the biggest headache for the PM, Sir Vince added: "How many of the heads of government that she telephoned over the weekend have indicated they would consider the Irish backstop dispensable?"
Mrs May said her discussions have consistently shown there should be a backstop to ensure there is no hard border between Northern Ireland and Ireland, noting concerns raised by MPs have been over the permanence of the arrangement.
She said: "A number of European leaders who I have spoken to have indicated that they are open to discussions to find a way to find reassurance to members of this House on that point."
Commons Speaker John Bercow earlier dished out a telling off to ministers, saying it was "deeply discourteous" to delay the planned Brexit deal vote.
He urged the Prime Minister to hold a vote on the matter before "unilaterally" deciding to postpone MPs having their say, saying it would be the "courteous, respectful and mature" thing to do.
Mr Bercow intervened following Mrs May's statement to criticise Number 10 for leaking their plans in advance of telling the House, saying the vote was being delayed at "an inordinately late stage".
He added: "Halting the debate after no fewer than 164 colleagues have taken the trouble to contribute will be thought by many members of this House to be deeply discourteous."
Mr Bercow said many MPs had complained to him already about the Government's plans "in the most forceful terms".
DUP Westminster leader Nigel Dodds said the Prime Minister's reassurance "simply is not credible" and the Government was in "an impossible position" without changes to the backstop.
His DUP colleague Sammy Wilson (East Antrim) said the EU's chief negotiator Michel Barnier and Irish premier Leo Varadkar have "slapped down" the idea of any renegotiation of the deal, adding: "The Prime Minister may be prepared to be humiliated by arrogant EU officials and by Irish politicians, but does she not realise that every time she comes back with her tail between her legs she humiliates the British people.
"When will she stand up to the EU? And if she's not prepared to stand up to the EU then let her have the vote of this House to tell them what we think of their rotten deal."
Mrs May, in her reply, said "we have stood up to the European Union", including on preventing the UK being separated into two customs territories.
DUP MP David Simpson (Upper Bann) also urged Mrs May to "admit" that Northern Ireland had had to be made the "sacrificial lamb to placate the Irish Republic and the EU" to ensure her deal got to this stage, something Mrs May denied.
Mrs May sidestepped questions from her own benches about how and when she would be rearranging the so-called "meaningful vote".
Tory Remainer and former education secretary Justine Greening asked whether she intended on pushing back the date as far as March 28 next year – the day before Brexit Day.
Mrs May said: "I do not believe the scenario she has set out is the correct one... I believe it is right we should be recognising the concerns raised in this House and attempting to find a way through those concerns and to resolve those concerns."
SNP MP Peter Grant (Glenrothes) criticised Mrs May's "red lines" on Brexit, adding: "If the Prime Minister will not accept it's time for the red lines to go, surely it's time for the Prime Minister to go."