LONDON (AP) — Four of Boris Johnson’s most senior staff quit on Thursday, triggering new turmoil for the embattled British prime minister.

Johnson’s office said chief of staff Dan Rosenfield and principal private secretary Martin Reynolds had both tendered their resignations. Director of Communications Jack Doyle and senior adviser Munira Mirza also said they had left Downing Street.

Reynolds is a key figure in the “partygate” scandal over lockdown-breaching parties held by Johnson and his staff during the coronavirus pandemic. He sent an invitation to about 100 staff to a “bring your own booze” garden party in May 2020, when Britons were banned from socializing in groups as part of restrictions to slow the spread of COVID-19.

The garden gathering is one of 16 alleged parties under investigation by senior civil servant Sue Gray. A dozen of the events are also being investigated by the Metropolitan Police.

This week Gray released an interim report looking at the four parties police are not investigating. She found that “failures of leadership and judgment” allowed events to occur that “should not have been allowed to take place” and described a Downing Street operation marked by excessive drinking and dysfunctional dynamics.

Johnson has apologized and pledged to fix the problems in his office, but has not admitted personal wrongdoing.

The prime minister's grip on power has been shaken by revelations that his staff held “bring your own booze” office parties, birthday celebrations and “wine time Fridays” in 2020 and 2021 while millions in Britain were barred from meeting with friends and family.

Lawmakers in Johnson's Conservative Party are mulling whether to seek a no-confidence vote in the leader who won them a big parliamentary majority just over two years ago. Under party rules, such a vote is triggered if 15% of party lawmakers — currently 54 people — write letters calling for one. If Johnson lost such a vote he would be replaced as party leader and prime minister.

It’s not known how many letters have been sent, though a handful of lawmakers said this week that they were seeking a no-confidence vote. Conservative discontent grew after Johnson accused opposition Labour Party leader Keir Starmer in the House of Commons on Monday of “failing to prosecute Jimmy Savile” when he was the U.K.’s director of public prosecutions. Savile was a veteran television personality who was revealed after his death in 2011 as one of Britain's worst serial sexual abusers.

Starmer said it was “a ridiculous slur peddled by right-wing trolls,” and some Conservatives also recoiled at the attack. Mirza, who has worked for Johnson since he was mayor of London a decade ago, resigned over the Savile comment.

“You are a better man than many of your detractors will ever understand, which is why it is so desperately sad that you let yourself down by making a scurrilous accusation against the leader of the opposition,” she wrote in a resignation letter, published by the Spectator magazine — of which Johnson is a former editor.

As Johnson’s troubles mounted Thursday, a government minister, Chief Secretary to the Treasury Simon Clarke, was asked by Channel 4 news whether it felt like the “last days of Rome” in Downing Street.

“The last days of Rome, I think, were more fun,” he said.