Allies of Boris Johnson have insisted he will carry on as Prime Minister even if significant numbers of Tory MPs refuse to back him in a confidence motion on Monday night.

Jacob Rees-Mogg claimed victory by a single vote will be enough for the Prime Minister to continue, despite the damage that would be done to his authority by such a major revolt.

The Prime Minister was informed on Sunday that he will face a confidence vote as a result of Tory discontent over the lockdown-busting parties in No 10 and the direction of his leadership.

Sir Graham Brady, the chairman of the backbench 1922 Committee, confirmed he had received the 54 letters from Conservative MPs needed to trigger the vote.

The secret ballot will take place at Westminster on Monday between 6pm and 8pm, with the count to take place immediately afterwards.

A steady stream of Tory MPs called publicly for the Prime Minister to stand down in the wake of Sue Gray’s report into breaches of the Covid regulations in No 10 and Whitehall.

But Tory concerns go far wider, covering the Prime Minister’s economic policies which have seen the tax burden reach the highest in 70 years, as well as his style of leadership.

In order to oust the Prime Minister, however, the rebels will need 180 MPs, and allies of Mr Johnson made clear he is determined to fight to stay on.

A succession of Cabinet ministers appeared on TV to voice support for the Prime Minister while Government colleagues and backbenchers also went on social media as part of a co-ordinated operation to bolster Mr Johnson’s position.

Brexit opportunities minister Mr Rees-Mogg said victory by a single vote would secure Mr Johnson’s job.

“One is enough, it’s no good saying that the rules of the party say something and then behind it unofficially there is some other rule that nobody knows and is invented for the purpose,” he told Sky News.

“I obviously want the Prime Minister to get as big a majority as possible, I think that would be helpful and it would close this matter down between now and the next general election, which would be good for the country, good for the Conservative Party, but one is enough.”

Northern Ireland Secretary Brandon Lewis said winning the vote “is victory” even if by a single vote.

“We live in a democracy and it’s absolutely right that a democratic decision is what we respect,” he said.

Attorney General Suella Braverman said “technically, yes” a single vote win would be enough for Mr Johnson to continue but “I’m sure that he will win with a larger margin than that”.

But in reality a major revolt would leave him damaged, perhaps fatally so, particularly with two by-elections on June 23 which could see further blows delivered to his leadership.

Sir Graham said he had informed Mr Johnson on Sunday that the threshold of 15% of the parliamentary party calling for a vote had been passed.

He indicated some Tory MPs had submitted letters post-dated until after the end of the Platinum Jubilee celebrations, which meant the contest would not clash with the extended bank holiday festivities.

Mr Johnson will address the 1922 Committee at 4pm on Monday as he battles to save his premiership and has also written to all Tory MPs.

In his letter Mr Johnson said: “Tonight we have the chance to end weeks of media speculation and take this country forward, immediately, as one united party.”

It is an opportunity to “draw a line” under the issue, he added.

“I do not believe our voters will lightly forgive us if – just when they need us most to be focusing on them – we appear once again to be focusing on Westminster politics.”

But Mr Johnson has already received the resignation of his anti-corruption tsar, John Penrose, who said the Prime Minister had breached the ministerial code over the partygate scandal and should quit.

In a further indication of the anger felt on the Tory benches, former minister Jesse Norman – who had been a long-standing supporter of Mr Johnson – published a scathing letter to the Prime Minister withdrawing his support.

Mr Norman said the Gray report showed Mr Johnson “presided over a culture of casual law-breaking at 10 Downing Street” and “to describe yourself as ‘vindicated’ by the report is grotesque”.

But his criticism of Mr Johnson was far broader, including the “ugly” policy of sending migrants on a one-way trip to Rwanda, the “unnecessary and provocative” privatisation of Channel 4, the ban on noisy protests which “no genuinely Conservative government” should have introduced, and the lack of a “sense of mission” in his administration.

“You are simply seeking to campaign, to keep changing the subject and to create political and cultural dividing lines mainly for your advantage, at a time when the economy is struggling, inflation is soaring and growth is anaemic at best,” Mr Norman said, warning that Mr Johnson continuing in office would be “potentially catastrophic for this country”.

Former foreign secretary Jeremy Hunt, who stood against Mr Johnson for the leadership in 2019, warned that the Tories would lose the next general election if the Prime Minister is allowed to remain in post.

“Having been trusted with power, Conservative MPs know in our hearts we are not giving the British people the leadership they deserve. We are not offering the integrity, competence and vision necessary to unleash the enormous potential of our country,” he said.

“And because we are no longer trusted by the electorate, who know this too, we are set to lose the next general election.”

He added: “Today’s decision is change or lose. I will be voting for change.”

But Cabinet ministers rallied round Mr Johnson – including those who could seek to replace him if he is forced out.

Foreign Secretary Liz Truss said: “The Prime Minister has my 100% backing in today’s vote and I strongly encourage colleagues to support him.”

Chancellor Rishi Sunak said “the PM has shown the strong leadership our country needs”.

Dozens of Tory MPs and ministers tweeted public messages of support on Monday morning – some including a document setting out some of the Prime Minister’s achievements and explaining why Mr Johnson has an “unmatched electoral record”.

Trade minister Penny Mordaunt, viewed as a potential leadership candidate, tweeted a message saying she would be at a D-Day commemoration event in Portsmouth, where she has her constituency.

But she told local newspaper The News: “I didn’t choose this prime minister, I didn’t support him in the leadership contest but he has always had my loyalty because I think that’s what you do when you have a democratic process – you select a leader and then you owe that person your loyalty.”

Mr Johnson spoke to Ukraine’s Volodymyr Zelensky on Monday morning as aides insisted he was carrying on with the job without being distracted by Tory infighting.

However, in a break from the usual protocol, Mr Johnson did not appear on Downing Street – where he would have faced a barrage of press questions – for the visit of Estonian counterpart Kaja Kallas.