Coronavirus lockdown rules had been “very hard for people to obey”, a Cabinet minister said as allies rallied round Boris Johnson over his attendance at a No 10 drinks event while social gatherings were banned.

The Prime Minister apologised for attending a “bring your own booze” party in the Downing Street garden in May 2020, during the first coronavirus lockdown, but insisted he believed it was a work event and could “technically” have been within the rules.

Members of the Government urged critics of the Prime Minister to wait for the findings of an official investigation into alleged lockdown-busting parties before passing judgment after Tory MPs began publicly calling for him to quit.

On Thursday night it was reported that two parties were held in Downing Street on April 16 2021, the day before the Duke of Edinburgh’s funeral amid tight coronavirus restrictions in Windsor.

The Telegraph reported that Mr Johnson did not attend the events, which were held to mark the departure of James Slack, the PM’s former director of communications, and one of the PM’s personal photographers.

It said around 30 people attended both events combined, at a time when Government guidance stated: “You must not socialise indoors except with your household or support bubble. You can meet outdoors, including in gardens, in groups of six people or two households.”

The Prime Minister pulled out of a planned visit to a vaccination centre in Lancashire on Thursday, where he would have faced questions from the media about his actions, because a family member tested positive for coronavirus.

The situation will keep him out of the public eye, with Downing Street saying he would follow advice to limit contacts “up to and including Tuesday of next week” despite not having to self-isolate because he is vaccinated.

Senior civil servant Sue Gray is examining a series of parties and gatherings held in No 10 and Whitehall in 2020 while coronavirus restrictions were in force.

Commons Leader Jacob Rees-Mogg told MPs: “The Prime Minister came here yesterday and apologised. He said that, with hindsight, it was not what should have happened or what he would have wanted to happen.

“It is being investigated by Sue Gray, a civil servant of the highest integrity and of the greatest reputation.

“But I think everybody understands, on all sides of the House, that people were obeying the rules, and that these rules were very hard for people to obey.”

Cabinet Meeting
Commons Leader Jacob Rees-Mogg said lockdown rules had been hard to obey (Aaron Chown/PA)

He suggested the wider inquiry into the Covid-19 pandemic should examine “whether all those regulations were proportionate, or whether it was too hard on people”, with people not being able to visit loved ones or  attend funerals.

No 10 said the Government had sought to find the “right balance” in the regulations but “there is no cost-free option”.

Cabinet minister Brandon Lewis also urged people to wait for the outcome of the Gray inquiry before making judgments on the Prime Minister’s future, adding that Mr Johnson believed he was within the rules.

“The Prime Minister has outlined that he doesn’t believe that he has done anything outside the rules. If you look at what the investigation finds, people will be able to take their own view of that at the time,” the Northern Ireland Secretary said.

Cabinet ministers publicly defended Mr Johnson after his apology on Wednesday, but the late interventions of Foreign Secretary Liz Truss and Chancellor Rishi Sunak – both tipped as potential successors – did little to instil confidence in his future.

While Mr Johnson endured a difficult session of Prime Minister’s Questions on Wednesday, Mr Sunak had notably spent the day away from London on a visit in Devon.

The Prime Minister’s official spokesman insisted the Cabinet fully supported Mr Johnson.

Asked about the delay in Ms Truss and Mr Sunak showing their support, the spokesman said: “What the Prime Minister wants and expects is the Cabinet to be focused on delivering on the public’s priorities.”

Asked if he believed he had the full support of his Cabinet, the spokesman said: “Yes.”

Culture Secretary Nadine Dorries later suggested the Chancellor may have been delayed coming to the Prime Minister’s defence because of poor connectivity during his trip.

She told Channel 4 News: “We know he doesn’t have great signal down there.”

But Mr Johnson faced open revolt from one wing of his party, as Scottish Conservative leader Douglas Ross urged him to quit, with almost all Tory MSPs supporting the call.

Mr Ross was dismissed as a “lightweight figure” by Mr Rees-Mogg following his intervention.

Mr Rees-Mogg  said Mr Ross held office in the Conservative Party so supporting the leader was the “honourable and proper thing to do”.

In Westminster, three other Tory MPs have publicly said Mr Johnson should go – Sir Roger Gale, former minister Caroline Nokes and chairman of the Public Affairs and Constitutional Affairs Committee William Wragg.

In the Commons on Wednesday the Prime Minister said he recognised “with hindsight I should have sent everyone back inside” instead of spending 25 minutes in the No 10 garden thanking staff for their work on May 20 2020.

Downing Street insisted he had not been sent an email from his principal private secretary, Martin Reynolds, encouraging colleagues to go to the garden for “socially distanced drinks” to “make the most of this lovely weather” – and urging them to “bring your own booze”.

Deputy Labour leader Angela Rayner suggested Ms Gray’s inquiry could leave Mr Johnson acting as “judge and jury” over his own conduct.

She said that any matters relating to ministers uncovered in the investigation would be dealt with under the ministerial code – of which the Prime Minister is ultimately in charge.

“So is the Prime Minister going to act as the judge and jury even though he’s also the man in the dock? Or will his Conservative colleagues find their integrity and finally act as executioners to his premiership?”

Ms Rayner has written to every Cabinet minister asking them to “come clean” about any gatherings they attended during lockdown.

The Metropolitan Police indicated any investigation by them would depend on evidence unearthed in the Gray inquiry.

The prospect of a police investigation had led to the possibility that the inquiry could be paused, but a Scotland Yard statement said: “The Met has ongoing contact with the Cabinet Office in relation to this inquiry.

“If the inquiry identifies evidence of behaviour that is potentially a criminal offence it will be passed to the Met for further consideration.”

Liberal Democrats leader Sir Ed Davey tweeted: “I’m stunned that (Met Commissioner Dame) Cressida Dick agrees with Boris Johnson that it really is one rule for him and another rule for everyone else. This country deserves so much better than an establishment stitch up.”

Meanwhile, Mr Johnson suffered another blow as deputy chief medical officer Professor Sir Jonathan Van-Tam – one of the Government’s most effective communicators during the pandemic announced his departure.

He will leave at the end of March to take up a new role as the pro-vice chancellor for the faculty of medicine and health sciences at University of Nottingham.