Transport secretary Grant Shapps has insisted Boris Johnson didn't believe that the boozy gathering with colleagues he attended during lockdown was a party after a leaked picture of the scene put renewed pressure on the prime minister.
Shapps said the event "in his [Johnson's] mind" wasn't a party and that the presence of his ministerial red box in the images leaked to ITV News on Monday supports that claim.
The pictures show Johnson drinking wine and raising a toast to a departing Downing Street member of staff, and were reportedly taken on 13 November 2020.
Covid regulations in place at the time banned people from different households mixing indoors.
Their publication has raised further questions about why Johnson was not fined for his attendance at the event, while others were, and whether he misled MPs in December 2021 by claiming in the House of Commons that no event took place.
Speaking to Sky News on Tuesday, Shapps argued that the prime minister believed his attendance at the event was part of his working day.
"Probably what happened was it was the end of a busy day, he walks down, he says 'cheers' to somebody who worked there, and walked out. To him, that's not a party," the minister said.
He added that it would be up for the privileges committee of MPs to decide whether he misled the House of Commons late last year. "This thing has been pretty well investigated, I would say, and you won't be short of further investigations," he told host Kay Burley.
"I suspect he probably left his office, walked into that office with his work, I imagine to take it back to his flat to do work later, and was literally asked by someone 'can you go and thank X who is leaving?', he thanks them and then walks out," said the transport secretary.
London mayor Sadiq Khan said this morning, however, that the leaked images raised new questions about Johnson's involvement in the event and that the Met Police should explain why it didn't give the prime minister a fixed penalty notice.
"The reason why it's important is we have police by consent. We need to have confidence in our police and the police must police and investigate without fear of favour," Khan said.
"I know from reading today's newspapers, from watching Sky News this morning, and from speaking to Londoners that there are many questions they have – including to Boris Johnson ,to explain how you can be raising a glass, having empty booze lying around, and it not being a party, and at the same time weeks later tell the House of Commons there wasn't a party."
Senior civil servant Sue Gray is expected to publish her full report into the events held at Downing Street and Whitehall during the coronavirus lockdown during this week.
Adam Payne is political editor of CSW's sister title PoliticsHome, where this story first appeared