Early verdicts on the Prime Minister’s future are beginning to seep in from Tory MPs after the Metropolitan Police determined Covid rules were breached in Whitehall.

Boris Johnson’s leadership was put under fresh pressure on Tuesday after it emerged an initial tranche of 20 fines will be issued over alleged lockdown-busting parties in government buildings.

It is expected that further fixed penalty notices (FPNs) could surface as officers continue to go through the evidence gathered.

The force is investigating 12 events, including as many as six Mr Johnson is said to have attended.

The PM is not thought to be among those set to receive a fine at this stage, as he is contesting the allegations and took advice from his personal lawyer on how to respond.

He came under intense pressure to quit as a result of partygate, but in recent weeks the war in Ukraine has seen Conservative MPs rally round their leader.

Now the Met’s intervention, confirming it believes laws were broken at the heart of Government, is likely to reignite the debate about his premiership.

Tory MP Andrew Bridgen said a “day of reckoning” may come in regard to the partygate scandal, but not at this moment in time.

Asked if the latest news changed his view on the situation, after he withdrew his letter of no confidence in the PM, Mr Bridgen said he would back Mr Johnson if there was a vote tomorrow.

He told the PA news agency: “If they were a vote (of) confidence in the Prime Minister tomorrow, in the national interest I’d have to support him – otherwise we’d be playing into the hands of Mr (Vladimir) Putin.”

He added: “There may be a day of reckoning in regard to the fallout from partygate, but it’s not now and it’s not for the foreseeable future either.”

Meanwhile, Matt Hancock – whose own time in the Tory cabinet was cut short when he was caught breaching social distancing rules he had helped to establish – also said the Prime Minister should stay, even if he is fined.

Asked if the PM can remain in his job, Mr Hancock told BBC News: “Yes, he can and he should. He has apologised and he’s acknowledged that there were problems and made changes in Downing Street.”

He added: “My judgment, without a shadow of a doubt, is that the best person to lead the country is Boris Johnson, who is delivering the sort of leadership that we need to keep us safe in very difficult times – that is absolutely clear to anybody who watches the news every night.”

Asked if he would say the same if Mr Johnson was issued with a fine, he said: “Yes… the police of course have got to look into it, but I think the broader judgment of who should be prime minister is based on the future and who is best placed to lead this country now.”

There may be a day of reckoning in regard to the fallout from partygate, but it's not now and it's not for the foreseeable future either

But veteran Tory MP Sir Roger Gale, who previously told PA that Mr Johnson was a “dead man walking” politically, said: “If it becomes apparent that the Prime Minister has been fined… then there clearly are serious questions that are going to have to be answered.”

He confirmed his letter of no confidence is still with the 1922 Committee, but current circumstances mean it is not “the time to change our leader”.

“If you’re saying does the probity of the Prime Minister of the United Kingdom matter, yes, it most certainly does,” he told Times Radio.

“If you’re saying, faced with the most serious international crisis since 1945, a terrifying potential circumstance, is now the time to change our leader, the answer is no it isn’t.”

Asked if the PM had been “pardoned” or “reprieved” in his mind for now, he said: “I think he’s been reprieved. First of all, of course, no names have been given and I’ve been approached by just about every media outlet known to man in the course of the day, and I’ve stoically refused to comment on this, because I don’t think there’s anything to comment on.

If it becomes apparent that the Prime Minister has been fined... then there clearly are serious questions that are going to have to be answered

“If it becomes apparent that the Prime Minister has been fined – and Downing Street has said that they will tell us if that’s so – then there clearly are serious questions that are going to have to be answered.

“But, and it’s a very big but. I believe that at the moment, faced with the international situation in Ukraine and potentially beyond… we need to be concentrating all our minds and all our efforts and all our unity across party.”

He added: “There will come a day of reckoning, but it’s certainly not now.”

It comes after No 10 insisted Mr Johnson did not mislead MPs when he told them no lockdown rules had been broken in Downing Street, despite the Met concluding the law was breached.

The PM’s official spokesman refused to be drawn on whether Mr Johnson would resign if he did get hit with a penalty, and also declined to say whether fined individuals would be able to carry on working in No 10.

But former chief whip Mark Harper suggested law-breaking civil servants or special advisers would have to be sacked.

The Tory MP tweeted a screenshot of the Civil Service Code, highlighting a passage saying they must “comply with the law”.