ITV News has published four photos, saying they were taken on 13 November 2020 at a leaving do for the PM’s director of communications, Lee Cain.

The police issued fines relating to No 10 gatherings on that date, but it is not known if they were for this event.

A No 10 spokeswoman said the Cabinet Office and the police had had access to information, including photographs.

After the leaked pictures were published, Labour’s deputy leader Angela Rayner said the PM had “demeaned his office” and “the British people deserve better.

She added: “Boris Johnson said repeatedly that he knew nothing about law-breaking – there’s no doubt now, he lied. Boris Johnson made the rules, and then broke them.”

A No 10 spokeswoman said that with the Met’s investigation concluded, senior civil servant Sue Gray would be publishing her report into the gatherings “in the coming days, at which point the prime minister will address Parliament in full”.

A raft of allegations about gatherings held in Downing Street and Whitehall throughout the pandemic led to a Metropolitan Police investigation into 12 events.

The inquiry concluded last week, with a total of 126 fixed penalty notices being issued to 83 individuals for parties held over eight separate dates.

Mr Johnson, his wife Carrie, and Chancellor Rishi Sunak all received one fine each for attending a birthday party thrown in the PM’s honour in June 2020.

But No 10 confirmed the PM was not facing any additional fines from the police.

On 8 December 2020, Labour MP Catherine West asked Mr Johnson in the Commons if a party had taken place in Downing Street on 13 November – though it is not clear if she was referring to the event photographed.

He replied: “No – but I am sure that whatever happened, the guidance was followed and the rules were followed at all times”.