Boris Johnson has ordered an investigation into claims Downing Street staff broke lockdown rules by holding a Christmas party last year and told MPs he was “furious” about footage apparently showing aides joking about it.

The Prime Minister apologised “unreservedly” for the offence caused by the footage of his then-spokeswoman Allegra Stratton at a mock press conference.

But he insisted he had been repeatedly assured “there was no party and that no Covid rules were broken”.

Mr Johnson said he had asked Cabinet Secretary Simon Case “to establish all the facts and to report back as soon as possible – and it goes without saying that if those rules were broken then there will be disciplinary action for all those involved”.

At Prime Minister’s Questions, Mr Johnson said: “I understand and share the anger up and down the country at seeing No 10 staff seeming to make light of lockdown measures, and I can understand how infuriating it must be to think that people who have been setting the rules have not been following the rules because I was also furious to see that clip.

“I apologise unreservedly for the offence that it has caused up and down the country and I apologise for the impression that it gives.

“But I repeat that I have been repeatedly assured since these allegations emerged that there was no party and that no Covid rules were broken, and that is what I have been repeatedly assured.”

The Prime Minister’s intervention followed a week of official insistence that no party took place on December 18 2020, when London was under Tier 3 restrictions – despite reports staff drank alcohol and exchanged Secret Santa gifts.

Allegra Stratton
Allegra Stratton laughs in the footage as she appears to rehearse answers to questions over a lockdown-busting Christmas party (PA)

Downing Street’s official line has now shifted with the announcement of the Case inquiry, with the Prime Minister’s press secretary declining to repeat the statement that “there was no party”.

She said “it wouldn’t be right to comment further” while Mr Case was investigating.

Downing Street would not initially confirm whether or not Mr Case was at the December 18 event, although Whitehall sources insisted he was not present.

Number 10 would not give a timetable for Mr Case’s investigation to conclude but the Prime Minister’s official spokesman said “we want it to be as soon as possible”.

The spokesman confirmed that Ms Stratton was still employed as an aide – she has been the spokeswoman for the Cop26 climate summit – and the Prime Minister still has confidence in her.

Labour leader Sir Keir Starmer said the Prime Minister’s apology “raises more questions than answers” as he had been “caught red-handed”.

“Millions of people now think the Prime Minister was taking them for fools, that they were lied to. They are right aren’t they?”

In response to questioning from Sir Keir, the Prime Minister agreed that any evidence uncovered by the Cabinet Secretary about parties in Downing Street would be handed over to police.

Leaked footage from No 10’s £2.6 million press briefing room emerged on Tuesday night which showed former press secretary Ms Stratton laughing as she appeared to rehearse answers to questions over a lockdown-busting Christmas party.

The video, which is reported to be from December 22 last year, refers to a party on “Friday” – which would have been December 18, the same day The Daily Mirror reported there was a staff party where games were played, food and drinks were served, and revelries went on past midnight.

The emergence of the footage – in which Ms Stratton and aides joked about how to respond to questions on the party – fuelled anger on the Tory benches about Mr Johnson’s Number 10 operation.

Sir Charles Walker, a former vice-chairman of the 1922 Committee of backbench Tory MPs, said the Government is likely to now find it “almost impossible” to introduce “very proscriptive” Covid-19 restrictions due to the saga.

He told Times Radio: “I think now that, going forward, any measures will be advisory. I think it would be very difficult to enshrine them in law and then once again ask our poor police forces to enforce them.”

Tory peer and former Conservative Party chairwoman Sayeeda Warsi said all those present at any party should quit.

In a sign of further potential difficulties for Mr Johnson, his former aide Dominic Cummings – who has become a prominent critic – suggested Mr Case’s investigation should look at parties in the Prime Minister’s Downing Street flat.

Downing Street said Mr Case’s investigation would only look at events related to the December 18 event, rather than the November 13 “flat party” Mr Cummings referred to.

In the footage obtained by ITV News, Ms Stratton and adviser Ed Oldfield, along with other aides, were filmed joking about a “fictional” Downing Street party.

During the rehearsal, filmed as part of a subsequently-abandoned plan for Ms Stratton to lead televised press briefings, one aide is heard saying: “It wasn’t a party, it was cheese and wine.”

“Is cheese and wine all right? It was a business meeting,” Ms Stratton replied, to laughter in the room.

Ms Stratton then noted “this is recorded”, adding: “This fictional party was a business meeting… and it was not socially distanced.”

The Metropolitan Police confirmed officers are reviewing the leaked video in relation to “alleged breaches” of coronavirus regulations.