Britain's Prime Minister Boris Johnson leaves Downing Street to attend the weekly session of Prime Ministers Questions Wednesday in London. British Prime Minister Boris Johnson is facing a wave of public and political outrage over allegations that he and his staff flouted coronavirus lockdown rules by holding a garden party in 2020 while Britons were barred by law from meeting up with more than one person outside their households. (AP Photo/Kirsty Wigglesworth)

LONDON (AP) — Boris Johnson’s office today apologized to the royal family for holding staff parties in Downing Street on the eve of Prince Philip’s funeral last year — the latest in a string of allegedly lockdown-breaching gatherings that are threatening to topple the British prime minister.

Farewell parties for Johnson’s departing spin doctor and another staffer, complete with late-night drinking and dancing, took place on April 16, 2021, the night before Queen Elizabeth II sat alone at the funeral of her husband because of social distancing rules in place to slow the spread of the coronavirus.

Johnson spokesman Jamie Davies said the government acknowledged that news of the gatherings had caused “significant public anger.”

“It’s deeply regrettable that this took place at a time of national mourning and No. 10 has apologized to the palace,” he said, using a term for the prime minister’s 10 Downing St. office.

Johnson’s former communications director James Slack apologized for the “anger and hurt” caused by his farewell party.

“I am deeply sorry, and take full responsibility,” added Slack, who left the government last year and is now deputy editor-in-chief of tabloid newspaper The Sun.

Johnson’s office said the prime minister wasn’t in Downing Street, where he both lives and works, on April 16, and had been unaware any gatherings were planned that day. Earlier this week, Johnson apologized for going to a separate gathering in the Downing Street garden in May 2020, when the U.K. was under strict lockdown.

The latest party revelations have appalled many in Britain because of the events’ timing. The Daily Telegraph, which broke the news, said Downing Street staff drank, danced and socialized late into the night, and that at one point an employee was dispatched with a suitcase to a nearby supermarket to buy more booze. The next day, the widowed queen sat alone in a church at Windsor Castle to say goodbye to her husband of 73 years.

Photos of the monarch, clad in black and wearing a face mask, became a powerful image of the isolation and sacrifice endured by many during the pandemic.

Members of Johnson’s Conservative government have expressed support for the prime minister following his admission on Wednesday that he attended a “bring your own booze” staff party in the garden of his Downing Street office in May 2020.

At the time people in Britain were banned by law from meeting more than one person outside their households as part of measures to curb the spread of the coronavirus. Millions were cut off from family and friends, and even barred from visiting dying relatives in hospitals.

Many Conservatives fear the “partygate” scandal could become a tipping point for a leader who has weathered a series of other storms over his expenses, and his moral judgment.

The latest revelations are likely to prompt more Conservatives to join opponents and demanding that Johnson resign for flouting the rules the government imposed on the country as the coronavirus swept the U.K.

In a sign of growing anger in party ranks, the Conservative association in the staunchly Tory district of Sutton Coldfield in central England voted unanimously on Thursday night to withdraw its support from Johnson.

“The culture starts at the top, doesn’t it?” said Simon Ward, a Conservative local councillor. “And that’s the really disappointing point.

“We were asking people all over our country to make massive sacrifices, people in rural Sutton Coldfield to make massive sacrifices, over the last two years. I think we have the right to expect everybody in government and in those positions of leadership to follow those same rules and guidelines as well.”

Johnson said in his apology on Wednesday that he understood public “rage,” but stopped short of admitting wrongdoing, saying he had considered the gathering a work event to thank staff for their efforts during the pandemic.

Johnson urged people to await the conclusions of an investigation by senior civil servant Sue Gray into multiple alleged rule-breaking parties by government staff during the pandemic. Gray, a respected public servant who has investigated past allegations of ministerial wrongdoing, is expected to report by the end of the month.

The government says Gray’s inquiry is independent, but she is a civil servant and Johnson is, ultimately, her boss. Gray could conclude that Johnson broke the code of conduct for government ministers, though she does not have the power to fire him. Johnson has not said what he will do if she found he was at fault.

Johnson does not have to face voters’ judgment until the next general election, scheduled for 2024. But his party could seek to oust him sooner if it judges he has become toxic.

Under Conservative rules, a no-confidence vote in the leader can be triggered if 15 percent of party lawmakers write letters demanding it.

Roger Gale, a Conservative lawmaker who has long been critical of Johnson, said he had already submitted a letter calling for a leadership challenge.

“I do think that minds are now, over this weekend, being focused upon the need to take the necessary action,” he said. “I clearly don’t know, and I shouldn’t know, how many of my colleagues have put in letters … but I believe that there is some momentum which is growing.”

Foreign Secretary Liz Truss — often cited as a potential successor to Johnson — said she understood “people’s anger and dismay” at the party revelations.

But she said “I think we now need to move on.”