Boris Johnson has paid a fine for attending his birthday bash in Downing Street and offered a “full apology” for the lockdown-busting event.

The Prime Minister said it “did not occur” to him that the gathering in the Cabinet Room on June 19 2020 to mark his 56th birthday was a violation of coronavirus rules.

However, he said that after being issued with a fine as part of a Metropolitan Police investigation into alleged parties at the heart of the Government during the pandemic he “now humbly accepts” he did breach Covid-19 laws.

Scotland Yard, according to a statement published by No 10, said Mr Johnson had been fined because “on June 19 2020 at the Cabinet Room…. between 1400 and 1500” he had been part of “a gathering of two or more people indoors”, which was banned at the time.

The Prime Minister, speaking to broadcasters at Chequers, said he “fully respects” the outcome of the police investigation and that he accepted “in all sincerity that people had the right to expect better” from him.

Outlining the busy nature of the day the fine related to, Mr Johnson said he chaired eight meetings in No 10 and followed them up with a four-hour round trip to a school in Hemel Hempstead, Hertfordshire.

He said: “There was a brief gathering in the Cabinet Room shortly after 2pm lasting for less than 10 minutes, during which people I work with kindly passed on their good wishes.

“And I have to say in all frankness at that time it did not occur to me that this might have been a breach of the rules.”

He added: “I now humbly accept that I was.

“But I think the best thing I can do now is, having settled the fine, is focus on the job in hand. That’s what I’m going to do.”

Asked if he thought more fines were coming his way, he said the media would be among the first to know.

Scotland Yard on Tuesday announced a further tranche of fixed-penalty notices (FPNs) in relation to Operation Hillman, which is probing possible Covid breaches in Downing Street and Whitehall, with more than 50 fines referred to the Acro Criminal Records Office since the inquiry started.

No 10 followed on by confirming that both the Prime Minister and the Chancellor were among those to be fined.

A spokeswoman for Carrie Johnson, the Prime Minister’s wife, also announced that she too had been fined.

Like her husband, her FPN was in relation to the June 2020 birthday gathering at which, according to Northern Ireland minister Conor Burns, Mr Johnson was “ambushed with a cake”.

Reports have suggested that up to 30 people attending the do and sung Happy Birthday in the Cabinet Room.

A spokesperson for Mrs Johnson said the former Tory director of communications had paid the fine, which is understood to have been £50 if settled within 14 days.

“Whilst she believed that she was acting in accordance with the rules at the time, Mrs Johnson accepts the Metropolitan Police’s findings and apologises unreservedly,” her spokeswoman said.

The PA news agency understands Rishi Sunak has also paid the penalty.

The Prime Minister has faced renewed calls to resign following the No 10 announcement that he had been slapped with a punishment for breaching coronavirus laws.

Labour leader Sir Keir Starmer, a former director of public prosecutions, said the police’s decision marked the “first time in the history of our country that a prime minister has been found to be in breach of the law”.

Speaking in Preston, he accused Mr Johnson of “repeatedly” lying about what happened behind the famous black door of No 10.

Sir Keir also argued that the Tory leader and Mr Sunak had “dishonoured” the sacrifices made by Britons who did follow the rules during the pandemic.

“The British public made the most unimaginable, heart-wrenching sacrifices, and many were overcome by guilt,” he said.

“But the guilty men are the Prime Minister and the Chancellor.

“Britain deserves better, they have to go.”

Labour has joined the chorus of demands for the Commons to be recalled from its two-week Easter break and allow Mr Johnson to “tender his resignation” in person to MPs.

The push for a recall has also been made by the Liberal Democrats and Plaid Cymru, while Scottish First Minister Nicola Sturgeon has been among those of prominence to demand the PM quits.

The Cabinet ministerial defence of Mr Johnson started with Culture Secretary Nadine Dorries, who argued that the Tory leader had “been clear about what happened” during the Cabinet Room gathering in 2020 and had “offered a full apology”.

“It was a brief gathering in the Cabinet Room, less than 10 minutes during a busy working day,” said Ms Dorries.

“PM is at his best when delivering on the priorities of the British people which he will continue to do.”

Treasury minister Simon Clarke also offered his “full support” to both the Prime Minister and Chancellor.

Mr Sunak has yet to comment since his fine was confirmed.

It comes as a poll found that a majority of people in Britain think the Prime Minister should resign after being issued with a Covid fine.

A snap YouGov poll of 2,460 adults taken on Tuesday found that 57% of people think he should go, with the same proportion thinking the same about the Chancellor.