The Prime Minister on Tuesday denied an allegation by former chief adviser Dominic Cummings that he intentionally misled MPs after being told the May 2020 event would breach coronavirus guidance.
In a major interview, Mr Johnson revealed he testified to the Whitehall inquiry into a series of allegations that “nobody told me that what we were doing was against the rules” to the “best of my recollection”.
He insisted he does “humbly apologise to people for misjudgments that were made” as he faces public calls to resign over the so-called “partygate” affair, including from six of his own Tory MPs.
But Labour said Mr Johnson “set the rules” and “didn’t need anyone to tell him that the party he attended broke them”.
As Chancellor Rishi Sunak refused to give the Prime Minister his unequivocal backing, Mr Johnson made his first public appearance after reducing his contacts last week, when No. 10 said a family member had tested positive for Covid-19.
Asked if he had lied to Parliament over the parties as he visited a north London hospital, Mr Johnson said: “No. I want to begin by repeating my apologies to everybody for the misjudgments that I’ve made, that we may have made in No 10 and beyond, whether in Downing Street or throughout the pandemic.
“Nobody told me that what we were doing was against the rules, that the event in question was something that … was not a work event, and as I said in the House of Commons when I went out into that garden I thought that I was attending a work event.”
Mr Johnson said he “can’t imagine why on Earth it would have gone ahead, or why it would’ve been allowed to go ahead” if he had been told it was anything but a “work event”.
“I do humbly apologise to people for misjudgments that were made, but that is the very, very best of my recollection about this event,” he said.
“That’s what I’ve said to the inquiry.
“I carry full responsibility for what took place, but nobody told me. I’m absolutely categorical, nobody said to me this is an event that is against the rules.”
Mr Johnson insisted he only saw the “bring your own booze” invite his principal private secretary Martin Reynolds sent to more than 100 staff “the other day … when it emerged”.
He declined to say whether he would resign if it was proved he did intentionally mislead Parliament, instead pleading for patience ahead of senior civil servant Sue Gray delivering the verdict of her partygate inquiry, which is not expected until the end of this week at the earliest.
Mr Johnson appeared distressed as he faced questions about two events in No. 10 last April on the eve of the Duke of Edinburgh’s funeral, during which the Queen sat alone as she mourned.
The Prime Minister audibly breathed heavily behind his mask as he said: “I deeply and bitterly regret that that happened.
“I can only renew my apologies both to Her Majesty and to the country for misjudgments that were made, and for which I take full responsibility.”
In a blog post on Monday, Mr Cummings said he was willing to “swear under oath” Mr Johnson lied when claiming he did not know in advance that the May 20 2020 event would be a “drinks party”.
He said he and another senior official warned Mr Reynolds the event outlined in his invitation would be against coronavirus rules.
“I said to the PM something like ‘Martin’s invited the building to a drinks party, this is what I’m talking about, you’ve got to grip this madhouse’ – the PM waved it aside,” Mr Cummings wrote on his blog.
“The events of May 20 alone, never mind the string of other events, mean the PM lied to Parliament about parties.
“Not only me, but other eyewitnesses who discussed this at the time would swear under oath this is what happened.”
Deputy Labour leader Angela Rayner said Mr Johnson “clearly knows it’s the end of the road” as she renewed a demand for him to do the “decent thing and resign”.
“He’s the Prime Minister, he set the rules, he didn’t need anyone to tell him that the party he attended broke them,” she said.
Meanwhile, Mr Sunak insisted he had accepted the Prime Minister’s explanation, saying he supports his appeal for patience while the inquiry is ongoing.
But, pressed by broadcasters whether he supports the Prime Minister unequivocally, the possible leadership contender abruptly broke off the interview and walked off with his microphone still attached.
Earlier, Deputy Prime Minister Dominic Raab insisted Mr Cummings’ claims were “nonsense”, but accepted Mr Johnson would “normally” be expected to resign if he intentionally misled Parliament.
Mr Raab told Times Radio: “The suggestion that he lied is nonsense. He’s made it very clear to the House of Commons that questions on this … that he thought it was a work event.”
But the Cabinet minister was pressed on what would be expected if Mr Johnson had lied to the Commons.
“If it’s lying, deliberate in the way you describe, if it’s not corrected immediately, it would normally under the ministerial code and the governance around Parliament be a resigning matter,” he told BBC Radio 4’s Today programme.
Downing Street denied that Mr Johnson lied to Parliament, but seemed to accept it would be a resigning matter if he “knowingly” misled the House of Commons.