Three more Tories - Anthony Mangnall, Sir Gary Streeter and Tobias Ellwood - called for the Prime Minister to stand aside on Wednesday (3 February).
This was then followed on Friday (5 February) by a further two MPs - Nick Gibb and Aaron Bell - who called for him to resign and said that they had submitted letters of no-confidence.
Ms Gray’s report criticised “failures of leadership and judgment” by parts of No 10 and the Cabinet Office.
It was also revealed that out of the 16 events she looked into, 12 are now subject to a Metropolitan Police investigation.
Mr Johnson reportedly attended as many as six of those possible gatherings being looked at by officers.
A host of Conservative MPs have now publicly called for the Prime Minister to resign, with several admitting that they have submitted no confidence letters.
Here we take a look at the Tories who have called for Mr Johnson to stand aside.
List of Tory MPs who have called for Boris Johnson to resign
The former education minister, writing in The Telegraph, said that his constituents were “furious about the double standards” and he said the Prime Minister had been “inaccurate” in statements to the Commons.
The MP for Bognor Regis and Littlehampton said he had submitted his letter of no confidence, and added: “To restore trust, we need to change the Prime Minister.”
The 2019 Red Wall MP has declared publicly he has submitted a letter calling for a vote of no confidence in his leader.
In a statement, he said: “The breach of trust that events in No 10 Downing Street represent, and the manner in which they have been handled, makes his position untenable.”
In an emotional question in the Commons on Monday following publication of the Sue Gray report into lockdown parties, Mr Bell asked Mr Johnson if he thought he was a “fool” for following Covid restrictions at his grandmother’s funeral.
The Scottish Conservative leader and MP for Moray has called for the Prime Minister to quit.
He has also been joined by all 31 Tory MSPs in calling for Mr Johnson’s resignation, according to reports.
Mr Ross confirmed he had sent a letter of no confidence to the chairman of the 1922 Committee of backbench Tory MPs, Sir Graham Brady.
He said Mr Johnson’s position was “no longer tenable” and “I don’t think he can continue as leader of the Conservatives”.
Sir Roger Gale
The Conservative North Thanet MP told the PA news agency “you don’t have bring-a-bottle work events in Downing Street, so far as I’m aware.”
He added: “I think the time has come for either the Prime Minister to go with dignity as his choice, or for the 1922 Committee to intervene”.
Mr Wragg, a vice-chairman of the 1922 Committee and MP for Hazel Grove, told BBC Radio 4’s PM programme: “The Prime Minister’s position is untenable and I don’t believe 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.
“I think it is for the Conservative Party – if not the Prime Minister in fact – to make that decision.”
The MP for Romsey and North Southampton told ITV’s Peston the Prime Minister had “put himself in an impossible position”.
She said Mr Johnson “did a fantastic job” at the 2019 election, but added: “Now regretfully, he looks like a liability, and I think he either goes now, or he goes in three years’ time at a general election, and it’s up to the party to decide which way around that’s going to be.
“I know my thoughts are that he’s damaging us now.”
The Conservative MP for North West Leicestershire has publicly announced that he had submitted a letter of no confidence in the Prime Minister on Thursday (13 January) night.
He was the fifth MP to confirm that they had written to Sir Graham, the chair of the 1922 Committee, calling for a vote on the PM’s future as head of the party.
Mr Bridgen told BBC Newsnight: “With a heavy heart, I have written a letter to Sir Graham Brady indicating that I have no confidence in the Prime Minister and calling for a leadership election.”
The former children’s minister wrote in a Facebook post that Mr Johnson’s position had become “untenable” and that his “resignation is the only way to bring this whole unfortunate episode to an end”.
Apologising for the “great hurt” caused to his constituents by the allegations, the East Worthing and Shoreham MP added: “Frankly the issue for me is not how many sausage rolls or glasses of prosecco the Prime Minister actually consumed.
“The reason for my conclusion in calling for him to stand down is the way that he has handled the mounting revelations in the last few weeks.
“Obfuscation, prevarication and evasion have been the order of the day when clarity, honesty and contrition was what was needed and what the British people deserve.”
The former Brexit secretary called for Mr Johnson’s resignation during PMQs, telling him “in the name of God, go.”
Mr Davis said he has defended the Prime Minister for weeks from angry constituents, reminding them of the “successes of Brexit”.
He then told the House of Commons: “I expect my leaders to shoulder the responsibility for the actions they take.
“Yesterday, he did the opposite of that so I will remind him of a quotation which may be familiar to his ear – Leopold Amery to Neville Chamberlain: You have sat too long here for any good you have been doing. In the name of God, go.”
The chairman of the Defence Select Committee said the Prime Minister had lost his support.
He urged Mr Johnson to “call a vote of confidence rather than waiting for the inevitable 54 letters to be eventually submitted”.
Telling Sky News it was “horrible” for MPs to have to defend partygate, he confirmed on February 2 that he had presented his letter to the 1922 Committee.
The Waveney MP has confirmed that he had sent a letter to Sir Graham, tweeting: “After a great deal of soul-searching, I have reached the conclusion that the Prime Minister should resign.”
Mr Aldous said he had “never taken such action before” but that he believed it was “in the best interests of the country” for a change at the top.
In an intervention after Mr Johnson’s statement to the House of Commons following the publication of the update on the Gray inquiry on January 31, the former Cabinet minister told the No 10 incumbent he “no longer enjoys my support”.
The Totnes MP, who entered Parliament in 2019, criticised Mr Johnson’s “actions and mistruths” in a social media post.
He also confirmed that he had joined colleagues in calling for a no confidence vote.
“Standards in public life matter. At this time I can no longer support the PM,” he tweeted.
Sir Gary Streeter
In a Facebook post, Sir Gary Streeter said he had formally called for a “motion of no confidence in the Prime Minister”.
The South West Devon MP said: “I cannot reconcile the pain and sacrifice of the vast majority of the British public during lockdown with the attitude and activities of those working in Downing Street.”
Sir Charles Walker
The vice chairman of the 1922 Committee told Channel 4 News on February 1 he would “applaud” Mr Johnson if he chose to stand down, but said it was “his decision”.
Other Tories who have called for Boris Johnson to resign
Baroness Sayeeda Warsi
The former co-chairman of the Conservative Party, who served in the coalition government, has called for Mr Johnson to go.
She tweeted: “Every minister, parliamentarian & staffer at any #downingstreetparty must resign NOW. No ifs no buts.
“The rule of law is a fundamental value - the glue that holds us together as a nation. Once that is trashed by those in power the very essence of our democracy is at stake.”
Baroness Ruth Davidson
The former leader of the Scottish Conservative Party backed the calls of her successor, Mr Ross, for the Prime Minister to go.
She tweeted: “A tough call to make. But the right one.”
Ms Davidson added: “Nobody needs an official to tell them if they were at a boozy shindig in their own garden.
“People are (rightly) furious. They sacrificed so much – visiting sick or grieving relatives, funerals. What TF were any of these people thinking?”
How many no-confidence letters have been sent to the 1922 committee?
The future of Mr Johnson’s premiership will depend on how many letters of no confidence are submitted by Tory MPs to Sir Graham.
The 1922 Committee chairman will not reveal how many letters he has received until the figure of 15% of MPs is reached - which will trigger a confidence vote.
With the current parliamentary make up this would mean 54 letters.
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