ITV News Political Correspondent Carl Dinnen reports on the explosive fallout resulting from the leaked press conference video that has led to fury among MPs from across the political spectrum
The prime minister has asked Cabinet Secretary Simon Case to investigate whether events in Number 10 last year broke strict lockdown rules, adding how he was furious to see the leaked video.
Speaking at PMQs, Mr Johnson said he was "furious" to see the leaked recording, which shows senior Downing Street staff laughing about throwing a festive bash in Number 10 four days after the event is alleged to have taken place last December.
But added he has been "repeatedly reassured" there was no party.
The prime minister agreed to provide the Metropolitan Police with any information the government has about Downing Street parties, with the force currently considering whether it should investigate.
Labour leader Sir Keir Starmer said the PM had been "caught red-handed" and questioned the need for an investigation, telling MPs it is "it is obvious what happened".
"We have all watched the video of the prime minister's staff including his personal spokesperson. They knew there was a party, they knew it was against the rules, they knew they couldn't admit it, and they thought it was funny."
He added: "The prime minister has been caught red-handed. Why doesn't he end the investigation right now by just admitting it?"
Today Johnson told MPs: "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."
Watch PMQs in full:
The alleged party is said to have taken place on December 18 while millions of people in the UK were being forced to avoid socialising because of coronavirus lockdowns.
At the time London was in Tier 3 restrictions, under which the law clearly stated: “No person may participate in a gathering in the Tier 3 area which consists of two or more people, and takes place in any indoor space.”
It has been questioned whether Cabinet Secretary Mr Case is the right person to lead an inquiry into the alleged party, given suggestions that may have actually attended himself.
Number 10 would not confirm or deny whether Mr Case was at the party when speaking to MPs after Prime Minister's Questions.
Peston: 'This is serious- lets be under no illusion'
The indication following PMQs is that the prime minister is blaming his staff for the alleged party and not accepting blame himself, however that same strategy will be harder to maintain if allegations made by his former chief aide turn out to be true.
Dominic Cummings wrote on Twitter that there had been a party in the prime minister's Downing Street flat on November 13 last year.
Mr Johnson denied there was a party but said "I'm sure that, whatever happened, the guidance was followed at all times".
Meanwhile, the most senior civil servant at the Department for Education has apologised for a party attended by several members of staff on December 10 last year.
Susan Acland-Hood admitted attending the party, which she said was instigated by former Education Secretary Gavin Williamson.
She told the Commons Public Accounts Committee: "While this was a work-related gathering, looking back we accept that it would have been better not to have gathered in this way at that particular time."
SNP Westminster leader Ian Blackford called on the PM to resign, saying he "can no longer lead on the most pressing issue facing these islands".
Alongside intense political pressure over the alleged party, Mr Johnson is considering whether he should bring in more coronavirus restrictions to combat the Omicron variant.
It is understood a press conference will be held this evening to update the public on any plans for fresh measures.
But Labour leader Sir Keir questioned how the public could expected to follow the rules if they believe they have not been obeyed by those making them.
Sir Keir said "even the prime minister must understand the damage he's done to his credibility in enforcing the rules now and in the future".
He added: "The British people put the health of others above themselves and followed the rules. Isn't the prime minister ashamed that his Downing Street couldn't do the same?"
There was also dissent from the PM's own backbenches, with Conservative MP William Wragg calling any plan for new restrictions a "diversionary tactic".
He said: "Covid passes will not increase uptake of the vaccine but will create a segregated society. Is the Prime Minister aware that very few will be convinced by this diversionary tactic?"
Mr Johnson replied: "No decisions will be taken without consulting the Cabinet."
On the PM's apology, Sir Keir said it "raises more questions than answers".
The Labour leader said: "Millions of people now think the prime minister was taking them for fools, that they were lied to. They are right aren't they?"
Mr Johnson replied: "I think he missed what I said. I apologise for the impression that has been given that staff in Downing Street take this less than seriously. I am sickened myself and furious."