Dr Neil Hudson, the MP for Penrith and the Borders, said he “categorically will not defend the indefensible” and described the behaviour of Mr Johnson and Rishi Sunak, the Chancellor, who also received a fixed penalty notice, as “deeply damaging for our democracy”.

“Destabilising the UK Government would undermine international efforts to support the Ukrainian people and bring the despicable Russian invasion to an end,” he said.

“I will therefore be looking to the Prime Minister to show the statesmanship he has been showing with Ukraine, and outline a timetable and process for an orderly transition to a leadership election as soon as the international situation permits.”

Nigel Mills, the Conservative MP for Amber Valley in Derbyshire, and Craig Whittaker, the Calder Valley MP, called for Mr Johnson’s departure earlier in the week.

Speaking at a press conference in Kent on Thursday, the Prime Minister told reporters: “You are going to have to wait until I come to Parliament when of course I will set the record straight in any way that I can.”

Asked whether he could rule out resigning or facing any further fines, he said: “I redirect you to what I said earlier on, that won’t give you any particular surprise. I said quite a lot about this earlier in the week. I think I should wait until Parliament gets back to update Parliament fully.”

Forty-eight Tory backbenchers have signalled their support for Mr Johnson, including more than a dozen who were critical when it emerged that he had attended a garden drinks party during lockdown on May 20, 2020. The event was not investigated by the police.

“In terms of the ‘partygate’ fines and everything else, I’m afraid it’s all rather too long ago, rather too silly now, frankly, to be pursuing that any further,” Craig Mackinlay, the MP for South Thanet, told The Telegraph. “Time is a great healer – we’re talking about events that are close to two years ago. They’ve lost their potency now.”