Lockdown parties in No 10 on eve of Prince Philip's funeral
Downing Street staff held two parties the night before Prince Philip's funeral - at a time when Covid restrictions banned indoor mixing.
The events, first reported by The Telegraph, took place on 16 April 2021 and went on until the early hours, reports BBC.
Prime Minister Boris Johnson was not at either party - but it raises further questions about a culture of rule-breaking at Downing Street.
The PM is facing calls to resign from the opposition and some senior Tories.
He has urged MPs to wait for the outcome of an investigation into lockdown parties at No 10 by senior civil servant Sue Gray, which is expected as early as next week.
One of the events on 16 April was a leaving party for the PM's then director of communications James Slack.
A No 10 spokeswoman said Mr Slack "gave a farewell speech" to thank colleagues ahead of taking up a new role as deputy editor of The Sun newspaper.
He has apologised for the "anger and hurt" caused by the leaving event, and acknowledged it "should not have happened at the time that it did".
But he said he could not comment further as it had been referred to Sue Gray as part of her investigation.
The latest revelation comes as the prime minister faces anger from his own party over attending a drinks gathering in the Downing Street garden during the first lockdown.
Cabinet ministers have rallied round Mr Johnson, but five of his own MPs have called for him to step down.
Labour's deputy leader, Angela Rayner, said "the buck stops with the PM" over the "culture and behaviours" inside No 10.
According to the Telegraph, Mr Slack's leaving party coincided with another gathering in the No 10 basement for one of the PM's personal photographers.
The reported events were held at a time when the UK was in a period of national mourning, which ran from 9 April to 17 April, following the Duke of Edinburgh's death.