LONDON — British Prime Minister Boris Johnson is facing calls from senior Tories to stand down as prime minister after he admitted attending a drinks party during lockdown, BBC reported.

The PM apologized for the way he handled the event in the Downing Street garden in 2020 and said he understood the public's "rage" over it.

Cabinet members including deputy PM Dominic Raab rallied around Johnson.

But Scottish Tory leader Douglas Ross and MPs William Wragg, Caroline Nokes and Roger Gale called on him to go.

Ross, an MP and an MSP, said he had a "difficult conversation" with Mr Johnson after the PM apologized earlier on Wednesday in the House of Commons.

He said he would write to the 1922 Committee — which organizes Tory leadership contests - to register his lack of confidence in the PM.

"He is the prime minister, it is his government that put these rules in place, and he has to be held to account for his actions," he said.

If 54 backbench Conservative MPs send letters to the 1922 committee it will trigger a leadership challenge.

Ministers have urged MPs to wait for the outcome of an investigation by senior civil servant Sue Gray into alleged Covid-rule breaking at Downing Street parties, which they say will be published shortly.

Speaking to BBC Breakfast, Northern Ireland Secretary Brandon Lewis said: "You've got to let these investigations get to the full details and the full facts."

He said "with hindsight [the prime minister] regrets going out to the garden" and recognized the "frustration, anger and upset" about what people perceived to be happening at Downing Street, adding he "absolutely" offered his full support to the prime minister.

But Wragg, another backbencher, who chairs an influential select committee, said the prime minister's position was "untenable".

"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," he told BBC Radio 4's PM program.

And fellow Tory Caroline Nokes, who chairs another Commons committee, said the prime minister should resign now as he was "damaging the entire Conservative brand".

The former minister, who has previously been critical of Johnson's leadership, told ITV's Robert Peston: "Regretfully, he looks like a liability.

"And I think he either goes now, or he goes in three years' time at a general election."

At Prime Minister's Questions on Wednesday, Johnson sought to calm anger over reports he attended a "bring your own booze" party at the height of the first lockdown.

He admitted he was at the 20 May 2020 gathering for about 25 minutes, so that he could "thank groups of staff" for their hard work, but said he "believed implicitly that this was a work event"."

However, he added: "With hindsight I should have sent everyone back inside.

"I should have found some other way to thank them, and I should have recognized that - even if it could have been said technically to fall within the guidance — there would be millions and millions of people who simply would not see it that way."

Labour leader Sir Keir Starmer said the PM's explanation for his attendance was "so ridiculous that it's actually offensive to the British public" and he called on Johnson "to do the decent thing and resign".

The SNP's leader at Westminster Ian Blackford called on Tory MPs to force the PM out - and Lib Dem leader Sir Ed Davey said he had to go.

Sir Ed has written to the Metropolitan Police to ask them to investigate Johnson's attendance at the 20 May party.

The PM's statement was met with a mixed reaction from Conservative MPs, with Dan Poulter saying it was "not much consolation" for those who had worked on the frontline in the NHS.

But cabinet ministers rallied to Johnson's defense, including Raab, Education Secretary Nadhim Zahawi and Levelling Up Secretary Michael Gove, who said it was important to wait for Ms Gray's report to conclude.

Foreign Secretary Liz Truss and Chancellor Rishi Sunak - both tipped as potential successors to Johnson as leader — tweeted their support on Wednesday evening.

Truss said she stood behind the prime minister "100%", while Sunak Johnson was "right to apologize", adding that he supported the PM's call for "patience" while Gray completed her investigation.

Commons leader Jacob Rees-Mogg said those who were calling for Johnson were "people who are always unhappy" and dismissed Scottish Conservative leader Douglas Ross as "quite a lightweight figure".

The Conservative MP for Brigg and Goole, Andrew Percy, criticized Rees-Mogg's comments, saying: "As someone who apparently loves the Union, his personal attack on Douglas... is a gift to the petty nationalists in the SNP who want to break this country up."

It came as a poll for The Times by YouGov, which was carried out before Johnson's apology at Prime Minister's Questions, put Labour at a 10-point lead ahead of the Tories - the party's biggest lead since December 2013.