Boris Johnson’s most senior communications adviser addressed staff and handed out awards on the night of the alleged Downing Street party, it is understood.
Jack Doyle, the director of communications in Number 10, thanked staff working there “like he does every week”.
The political adviser in overall charge of Mr Johnson‘s communications also gave out “thank you awards” on the night of 18 December, Sky News understands.
ITV News was first to report Mr Doyle was present on the evening of 18 December 2020.
Mr Doyle has overseen the communication strategy which has seen Number 10 deny for a week that there was a party on 18 December, after the Daily Mirror first revealed details.
Following leaked footage of Number 10 aides laughing about an event, Mr Johnson has tasked the Cabinet Secretary Simon Case with investigating what happened and whether they were telling the truth.
Speaking at PMQs on Wednesday, the PM apologised and said he was “furious” at the footage, but told MPs he has been “repeatedly assured” no such gathering took place.
The footage, obtained by ITV News, is reported to be of a rehearsal for a TV media briefing from 22 December last year – four days after an alleged Christmas party took place in Number 10.
Senior Number 10 aides are heard jokingly referring to a “business meeting” and a “cheese and wine” event.
London had been put into Tier 3 restrictions on 16 December, preventing mixing indoors between households.