London, UK - British prime minister Boris Johnson has been ordered to pay a fine for attending his birthday bash in Downing Street, and offered a "full apology" for the pandemic lockdown-busting event.

Metropolitan Police have been investigating alleged parties thrown by UK government officials that took place at the height of the Covid-19 pandemic.

The probe, called Operation Hillman, found that officials breached Covid protocols, and more than 50 fines have been referred to the Acro Criminal Records Office.

New fines announced Tuesday have been issued to the prime minister in relation to a June 2020 birthday gathering at which, according to Northern Ireland minister Conor Burns, Johnson was "ambushed with a cake."

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Several others involved also received fines, including his wife Carrie Johnson and chancellor of the exchequer Rishi Sunak.

Johnson spoke to broadcasters at Chequers Court, the country house of the prime minister, and said he "fully respects" the outcome of the police investigation and that he accepts "in all sincerity that people had the right to expect better" from him.

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

The prime minister has faced renewed calls to resign following the announcement that he has been slapped with a punishment for breaching coronavirus laws.

Keir Starmer, leader of the opposition Labor Party, 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."

Starmer also argued that Rishi Sunak had "dishonored" the sacrifices made by Britons who did follow the rules during the pandemic.

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"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," he added.

Culture Secretary Nadine Dorries came to the prime minister's defense, explaining, "It was a brief gathering in the Cabinet Room, less than 10 minutes during a busy working day. [Johnson] is at his best when delivering on the priorities of the British people which he will continue to do."

Treasury Minister Simon Clarke also voiced his "full support" for Johnson and Sunak.

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.

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