At Prime Minister’s Questions in the Commons, Sir Keir asked Mr Johnson: “As millions of people were locked down last year, was a Christmas party thrown in Downing Street for dozens of people on December 18?”

The Prime Minister replied: “All guidance was followed completely.”

Sajid Javid encourages Christmas partygoers to take lateral flow tests

On the Health Secretary’s suggestion that partygoers should take Covid tests, Downing Street insisted the Government’s guidance had not changed, but that Britons had been “encouraged” throughout the pandemic to make use of state testing facilities.

The Prime Minister’s official spokesman said: “We do have a significant testing capacity and if people wanted further reassurance, they could use that.”

Mr Javid warned it “might take a bit longer than three weeks, it might be a bit sooner” for the Government to review the threat posed by the omicron variant.

He had vowed to reconsider the mask, self-isolation and travel rules introduced in recent days after three weeks, by December 20.

‘You can be too careful’ over Covid restrictions, say Tory MPs

His suggestion it could take ministers longer to gather data on omicron sparked alarm among lockdown-sceptic Tory MPs, who have demanded the Government scrap all new Covid restrictions on December 20 if there is no evidence by then that it is more dangerous than delta.

Steve Baker, deputy chairman of the Covid Recovery Group of lockdown sceptic Tory MPs, said the package of measures must be removed at the three-week review point unless there is proof of its need.

“I would scrap it on the basis there is insufficient evidence for making things worse for people. You can be too careful,” he said. “The Health Secretary really had better be sure that the collateral damage he is causing is worth it.

“This kind of goalpost shifting is groundhog day. Living with coronavirus at the present infection fatality rate really should be like living with flu. Of course, we don’t take LFDs for flu before going to parties.”

Sir Graham Brady, chairman of the 1922 Committee of backbenchers, agreed “there would be a good case” for removing the fresh restrictions on December 20 unless ministers have evidence justifying their continuation.

“We should move away from government mandate and towards people making their own choices with the best information,” he said.

“What we’ve seen throughout is where there has been legitimate cause for concern, people have taken their own precautions.”