The disclosure comes after the Prime Minister said that he was “sickened and furious” about the video of Ms Stratton, his former press secretary, and other No 10 staff joking about the event, which is alleged to have taken place in contravention of Covid restrictions in the run-up to Christmas last year. Senior Tories fear the fallout over the event and the leaked video has further damaged the party’s prospects in this week’s by-election in North Shropshire, where the Conservatives currently enjoy a 23,000 majority.

Douglas Ross, the Scottish Tory leader, said it seemed “undeniable” that “some sort of party” occurred on December 18, while London was in Tier 3 lockdown measures.

Government sources questioned why Mr Davies appeared to have emerged from the incident unscathed, when Ms Stratton had resigned and Ed Oldfield, the 24-year-old aide who fired questions at Ms Stratton, had also come under pressure to quit.

One Government source said: “A senior civil servant has been let off the hook and the special advisers have been thrown under the bus.” 

A Tory source added: “Unelected officials scolding MPs in public about following the rules whilst breaking them behind closed doors, attending illegal parties and making jokes at the public’s expense is exactly the sort of hypocrisy the public despises.”

Mr Davies is now Mr Johnson’s deputy official spokesman and head of news at No 10.

He can be heard intervening in the December 22 rehearsal of Ms Stratton’s planned press briefings, when Mr Oldfield asks the Prime Minister’s then press secretary about the December 18 party and she is stuck for a response.

Laughing, Ms Stratton initially states: “I went home”. Mr Oldfield then asks whether Mr Johnson would “condone having a Christmas party”, to which Ms Stratton replies: “What’s the answer?”

Mr Davies can then be heard stating: “It wasn’t a party, it was cheese and wine”.

“Is cheese and wine alright?” Ms Stratton asks. Mr Davies then appears to state: “No, I’m joking”.