Boris Johnson boasted "I'd do it again" when confronted over Partygate leaving drinks at a showdown with his backbenchers.
The Prime Minister appealed to Tory MPs to keep him power rather than indulge in "pointless fratricide" ahead of tonight's no confidence vote in his leadership.
In a speech to the backbench 1922 Committee, Mr Johnson dangled the vague prospect of tax cuts and suggested he would stay on even if he wins by one vote, according to MPs present.
He went on the defensive over Partygate when confronted by outspoken critic Mark Harper, who asked why MPs should continue to defend the indefensible” and demanded to know why the PM had tried to water down the ministerial code.
A source said the PM "pulled a face and looked hurt" at the line of questioning. But asked about his attendance at lockdown leaving drinks described Sue Gray's scathing report, Mr Johnson told MPs: "I'd do it again."
A Tory source sought to clarify that the PM meant he would thank staff again for their hard work - an excuse Mr Johnson used for attending lawbreaking leaving dos after Sue Gray's report.
The partying PM was only fined for one event - his lockdown birthday bash in June 2020 - but he attended several farewell gatherings where other attendees were fined.
Outside the meeting, a senior Conservative source said the PM had not addressed the looming Privileges Committee report into whether he misled Parliament over Partygate.
The source tried to downplay the events, adding: "Is there anyone here who has never got pissed in their lives".
He told reporters: "Even you might find other interesting things to talk about between now and September or whenever this kicks off that matter so much more to your viewers, listeners and readers than yet another inquiry into a bunch of events that...is there anyone here who has never got pissed, in their lives?
"Is there anyone who doesn't like a glass of wine to decompress?"
Mr Johnson spent around 27 minutes addressing his party, who will decide his fate in a crunch confidence vote tonight.
He must retain the support of 180 MPs to stay in Downing Street or he will be ousted and a full leadership contest will begin.
Speaking to his MPs, the PM warned them that Tory splits risked the "utter disaster" of Labour entering No10, propped up by the SNP.
"The only way we will let that happen is if we were so foolish as to descend into some pointless fratricidal debate about the future of our party," he told MPs according to a source present.
Outside the meeting, Brexit hard-man Steve Baker said the PM had to go.
He told reporters: "I can't move past the requirement to have at the very top of government, a culture of compliance with rules."
He added: "I told the Prime Minister, if he broke the law, he would have to go. He's clearly broken the law. He's clearly acquiesced in the law being broken. And so I must keep my word that I gave on the record, and I shall have to vote that he should go."
Asked if he thought the PM would survive the vote, Mr Baker said: "I think tonight, it's highly likely that he will formally win.
"But what that means over months ahead, I don't know. What I am certain of is that the Conservative Party's got to find a way to raise our standard of conduct in all things not only amongst ministers, but amongst backbenchers."
Brexit Opportunities Minister Jacob Rees-Mogg warned his mutinous colleagues they risked derailing Brexit if they oust the PM.
He said: “What I would say to Steve [Baker] is that he is risking the Brexit he fought so hard for because no other leader will deliver Brexit in the way than the Prime Minister.”
Mr Rees-Mogg said he was optimistic about the result and said Boris Johnson should remain PM even if he wins by just one vote.
He joked: “What do the French have for Breakfast … one oeuf is enough”.
A veteran backbencher said: "My feeling is that the PM will probably win but I'd guess the rebellion will be bigger than expected."