Boris Johnson's job remains in a precarious position after an update from civil servant Sue Gray.
The report found "failures of leadership and judgement" over Downing Street lockdown parties that "should not have been allowed".
In a statement to the House of Commons, the PM said he understood the anger felt across the country and in the House of Commons.
"I get it and I will fix it," he said.
The full report has not yet been published as alleged instances in Downing Street are under investigation from the Metropolitan Police.
Opposition MPs, and now several Tory members, did not see it this way.
So which Tories think Boris Johnson should resign?
What have Boris Johnson and Labour Party leader Keir Starmer said? Follow our live blog for all the latest odds, rumours and updates
The Tories who believe Boris Johnson should resign
So far, seven Tory MPs have called on the PM to resign publicly, along with 23 MSPs (Members of the Scottish Parliament).
BBC Newsnight revealed that "every single" Tory MSP think Johnson should quit, amounting to 31 in total.
All four MPs have indicated that a letter of no-confidence has been submitted, or will be submitted, to the 1922 Committee to force a leadership contest.
Douglas Ross
Significantly, leader of the Scottish Conservatives Douglas Ross joined in with the calls for Johnson's head.
Speaking to the BBC on, Ross said: "I said yesterday if the Prime Minister attended... on May 20 last year... then he couldn't continue.
"Today in the House of Commons he has accepted and admitted he was there.
"I don't think his position as Prime Minister and leader of the Conservative Party is tenable and he does need to resign."
Johnson supporter Jacob Rees-Mogg told Newsnight in response: "Douglas Ross has always been quite a lightweight figure."
Sir Roger Gale
Senior backbenchers also joined in on the calls for the PM to go.
Sir Roger Gale told LBC's Shelagh Fogarty: "I think it's serious. I think it's very serious indeed.
"And I frankly think that he's done a good job delivering certain things, but I think we've now got to the stage where frankly we have to find another leader."
William Wragg
Hazel Grove MP William Wragg is also Chair of the Public Administration and Constitutional Affairs Select Committee and said Johnson should resign.
The main defence currently employed by the PM and MPs is to wait until the findings of Sue Gray's inquiry.
Wragg questioned this idea and told BBC Radio 4's PM programme: "I don't think it should be left to the findings of a civil servant to determine the future of the Prime Minister and, indeed, who governs this country."
Caroline Nokes
Tories like Caroline Nokes are considering their chances in the next general election.
Support among Tory MPs in the 'red wall' Northern seats is strong. These were typically Labour-held seats that turned blue in 2019, which many believe to be due to a liking of the PM and his focus on Brexit.
In non-red wall seats, however, other considerations may come into play as Labour begin to pull away in the polls.
The Romsey and Southampton North MP told Peston: "There are a lot of MPs in Parliament who owe their seats to him.
"There are also MPs like me that recognise that when it came to winning that election in 2019, he did a fantastic job but now, regretfully, he looks like a liability."
"He is damaging the entire Conservative brand."
David Davis
Former Brexit Secretary David Davis chose the House of Commons for his turn to tell the PM to resign.
Channelling the words of Leo Amery, who dramatically told Neville Chamberlain to resign, David said: "I expect my leaders to shoulder responsibility for the actions they take.
"Yesterday, he did the opposite of that. So I will remind him of a quotation altogether too familiar to him of Leo Amery to Neville Chamberlain: "You have sat there too long for all the good you have done. In the name of God... go."
Tim Loughton
Tim Loughton, pro-Brexit MP for East Worthing and Shoreham said: "I have regretfully come to the conclusion that Boris Johnson’s position is now untenable, that his resignation is the only way to bring this whole unfortunate episode to an end and I am working with colleagues to impress that view on Number 10."
Andrew Bridgen
Andrew Bridge was a keen supporter of Johnson, backing him for the leadership and to succeed Theresa May in 2019.
After Partygate revelations came out, the North West Leicestershire wrote in The Telegraph: "As more and more revelations have been published, and I fear more are yet to come out, it is clear that not only were rules broken in Downing Street but that the initial response was to stretch the truth about them being broken too.
"Claims by the Prime Minister that he did not know that he was attending a party seem at best misguided and at worst cynical. So today I'm calling on the Prime Minister to stand down."
