Boris Johnson is facing fresh calls to resign in the wake of Sue Gray's scathing report on lockdown boozing in Downing Street.
Conservative MP Julian Sturdy broke ranks to say the report "clearly shows the Prime Minister has presided over a widespread culture of disregard for the coronavirus regulations".
The York Outer MP added: "While I thought it important to wait for the conclusion of the Metropolitan Police investigation and the publication of the Sue Gray report, I am now unable to give the Prime Minister the benefit of the doubt and feel it is in the public interest for him to resign."
Mr Sturdy's statement landed as the Prime Minister gave a speech to the 1922 Committee of Tory backbenchers to try win back the trust of his party.
Conservative backbenchers have been ominously quiet since the publication of Ms Gray's report this morning, which said Mr Johnson must "bear responsibility" for the boozy culture in No10 during lockdown.
But scores of Tory backbenchers abandoned the PM as he was defending himself in the Commons.
A number of MPs got up and left when Mr Johnson shift the tone from contrition to branding Keir Starmer "Sir Beer Korma" over the 'Beergate' row and accusing his opponents of being "obsessed" with the scandal.
Tory MP Tobias Ellwood, who has already called for the PM to resign, urged his party colleagues to act against the PM.
He said: “This is a damning report about the absence of leadership, focus and discipline in No 10 – the one place where you expect to find those attributes in abundance.
“I’ve made my point and my position very clear to the Prime Minister: he does not have my support.
“But a question I humbly put to my colleagues is ‘are you willing day in and day out to defend this behaviour publicly?"
Ex-Justice Secretary Robert Buckland also took the PM to task over misleading MPs, saying "the rules of this House are clear that anybody who comes here and deliberately lies and misleads this House should leave their position, resign or apologise".
Later, the PM tried to win over Tory MPs at a meeting of the 1922 Committee of backbench MPs.
Speaking afterward, Tory MP and Johnson loyalist Jonathan Gullis said he gave the PM ten out of ten for his performance, adding no one called for the PM to go at the meeting.
Party sources, meanwhile, said the PM did not want to spend another "second" on Partygate.
A friend of Mr Johnson's suggested the PM was bullish about his chances of surviving as party leader, saying it was "ludicrous" to suggest he should resign.
He said: "He has a massive mandate from the last election, he overwhelmingly won leadership of the Conservative Party.
"We're halfway through an electoral term and half of it has been taken up by wrestling through a global pandemic where he got all the big calls right.
"The idea that he should just pack up at this point is ludicrous."
Mr Johnson can only be ousted if his own MPs turn against him by pushing for a vote of no confidence in his leadership.
54 MPs need to send letters to the 1922 Committee chairman Sir Graham Brady to trigger a vote against the Prime Minister.
But then rebels must secure the support of 50% of Tories to oust him - and if he wins, he will get a year's reprieve.
