LONDON >> Prime Minister Boris Johnson said Tuesday he paid a fine from police for attending a lockdown-breaching birthday party in his official residence, making him the first British leader to be sanctioned for breaking the law while in office.

The fines for Johnson, his wife, Carrie, and Treasury chief Rishi Sunak brought a simmering crisis for the prime minister back to full boil, with opposition politicians immediately calling for his resignation.

Johnson and his Conservative government have faced growing outrage since allegations surfaced late last year that he and his staff flouted Britain’s pandemic restrictions and held office parties in 2020 and 2021 when millions in the country were barred from meeting with friends and family — or even attending funerals for their loved ones.

“I have paid the fine and want to offer a full apology,” Johnson said. “I understand the anger many will feel that I myself fell short when it came to observing the very rules which the government I lead had introduced to protect the public. I accept in all sincerity that people had the right to expect better.”

Downing Street said Johnson was being sanctioned for attending a “gathering of two or more people indoors in the Cabinet Room at 10 Downing Street” on June 19, 2020. The event was a surprise birthday party for the prime minister.

Johnson said the gathering lasted “less than 10 minutes,” and “at that time, it did not occur to me this might have been a breach of the rules.”

London’s Metropolitan Police force said it had issued at least 50 fines after investigating a dozen events held in 10 Downing St. and and other government buildings. They reportedly included “bring your own booze” office parties and “wine time Fridays” organized by Johnson’s staff.

The force did not identify the recipients or the size of the fines. But Johnson’s office confirmed shortly after that the prime minister and Sunak each received notice Tuesday that they would be issued with fines for an undisclosed amount. If paid promptly, such fines do not result in a criminal record.

Opponents, and some members of the governing Conservative Party, say Johnson should resign.

Thousands of people were fined between 60 pounds ($79) and 10,000 pounds ($13,200) by police for rule-breaking social gatherings during the pandemic.

“Boris Johnson and Rishi Sunak have broken the law and repeatedly lied to the British public,” said Keir Starmer, leader of the opposition Labour Party. “The Conservatives are totally unfit to govern. Britain deserves better.”

Opposition parties called for lawmakers to be recalled from their Easter break for a vote of no-confidence in Johnson.

The COVID-19 Bereaved Families for Justice group said “there is simply no way” that Johnson or Sunak can remain in their jobs.

“It’s still unbelievably painful to know that the Prime Minister was partying and breaking his own lockdown rules — while we were unable to be at our loved ones’ sides in their dying moments,” said the group’s spokesman Lobby Akinnola.

A total of 16 parties were investigated by a senior civil servant, Sue Gray, with a dozen of them also under investigation by the Metropolitan Police.

In January, Gray published a report into some of the gatherings, the ones not under criminal investigation. She said “failures of leadership and judgment” in Johnson’s government allowed events to occur that should not have happened.

The report said some of the gatherings showed a “serious failure to observe” standards for government, and some behavior at the parties were “difficult to justify” given how the public were asked to restrict their lives.

Johnson’s grip on power had appeared to be on a knife-edge earlier this year because of the scandal and the departure of several top aides. Allies feared “partygate” could become a tipping point for a leader who has weathered a series of other storms over his expenses, and his moral judgment.

Some Conservative lawmakers were openly calling for a no-confidence vote in their leader — something that can happen if 15% of Conservative lawmakers demand it.

But Johnson has hung on, partly because Russia’s invasion of Ukraine distracted public and political attention.

Johnson’s international image, battered by Britain’s messy exit from the European Union under his leadership, has been revived by his firm military, political and moral support for Ukraine. Johnson traveled to Kyiv last weekend to meet with President Volodymyr Zelenskyy.

Johnson might also benefit from the woes afflicting Sunak, the 41-year-old Treasury chief who has been seen as a potential rival and successor. The fine for Sunak comes as he also faces a backlash over the spiraling cost of living and questions about his financial arrangements and the tax status of his wealthy wife.

Jill Rutter, a senior fellow at the Institute for Government think-tank, said “partygate” had damaged the reputation of both the government and the civil service.

“The line, ‘It’s one rule for them and another law for the rest of us’ really does resonate,” she said.

Rutter said Johnson was probably safe for now, but could face fresh peril if the Conservatives take a hammering in next month’s local elections.

“And with the prime minister, there’s always a possibility that something else comes out,” she said. “So you wouldn’t say that it’s guaranteed plain sailing through to the 2023-2024 election. But I think we definitely premature to write him off now.”