Downing Street has apologised to Buckingham Palace for two staff parties in No 10 on the night before Prince Philip’s funeral.
The gatherings, first reported by The Telegraph, took place on 16 April 2021 and went on until the early hours.
The PM’s spokesman said it was “deeply regrettable that this took place at a time of national mourning”.
Boris Johnson was not at either party – but he faces questions over alleged Covid rule-breaking at No 10.
The latest party revelations led to a backlash from opposition parties, who contrasted the behaviour of No 10 staff with pictures of the Queen sitting alone at the Duke of Edinburgh’s funeral, due to Covid restrictions.
And Andrew Bridgen has become the fifth Conservative MP to publicly declare they have written to the chairman of the 1922 Committee – which organises Tory leadership contests – to say they have no confidence in the prime minister.
Fifty-four Conservative MPs have to write a letter to trigger a vote.
Meanwhile, the former head of the government’s Covid taskforce has apologised for having leaving drinks in the Cabinet Office when she left the civil service on 17 December 2020.
Kate Josephs, who is now the chief executive of Sheffield City Council, said she was “truly sorry” for “the anger that people will feel”.
In a statement on Friday, she added that the drinks event will also now form part of the ongoing investigation into gatherings in government.
Sources have confirmed that this was a separate event to a quiz held for the private office of Simon Case, the UK’s top civil servant, on the same evening.
The two staff get-togethers for Downing Street staff on 16 April last year happened at a time when Covid restrictions banned indoor socialising.
They have also been added to the list of gatherings in government buildings being investigated by senior civil servant Sue Gray.
After No 10 apologised for the events, Labour leader Sir Keir Starmer said: “This shows just how seriously Boris Johnson has degraded the office of prime minister.
“The Conservatives have let Britain down. An apology isn’t the only thing the prime minister should be offering the Palace today.
“Boris Johnson should do the decent thing and resign.”