LONDON — An exodus of senior officials from 10 Downing Street on Thursday deepened the crisis engulfing Prime Minister Boris Johnson, as he fought to hold on to power in the wake of a scandal over parties that breached lockdown restrictions.
Mr. Johnson’s chief of staff, private secretary, communications chief, and head of policy all resigned, leaving the top of British government rudderless at a time when Mr. Johnson is struggling to avert a mutiny in the ranks of his Conservative Party. About a dozen party lawmakers have called publicly for a no-confidence vote in the prime minister.
Some of the departures fulfilled Mr. Johnson’s promise to overhaul the Downing Street operation, following the release of a government report on Monday that criticized the office for “excessive” workplace drinking, citing 16 social gatherings — some of them now under police investigation — during periods when England was under strict lockdowns.
But the resignation of his policy chief, Munira Mirza, carried an extra sting. One of his longest-serving and most influential aides, Ms. Mirza sent the prime minister a sharply critical letter in which she said he made a “scurrilous accusation” against the leader of the opposition Labour Party, Keir Starmer.
That referred to claims Mr. Johnson had made in Parliament on Monday, linking Mr. Starmer, who is a former chief public prosecutor, to a failure to bring charges against Jimmy Savile, a popular television personality who died in 2011, having never been tried for a string of sex offenses that later came to light.
Mr. Starmer was not involved in the case and later ordered an inquiry into the failure of his department to take action. Following the exchange in Parliament on Monday, Mr. Johnson modified his comments, but Ms. Mirza said that the prime minister’s clarification, made on Thursday, fell short of a full apology.
“Even now,” she wrote, “I hope you find it in yourself to apologize for a grave error of judgment made under huge pressure.”
Mr. Johnson’s claim also drew criticism from the chancellor of the Exchequer, Rishi Sunak, whose words are being closely scrutinized because he is viewed as a potential candidate to replace Mr. Johnson as Conservative leader and prime minister if he is ousted.
“Being honest, I wouldn’t have said it, and I am glad that the prime minister clarified what he meant,” Mr. Sunak said at a news conference where he announced plans to try to cushion the blow of steep increases in household energy bills.
The departures of the chief of staff, Dan Rosenfeld, and the principal private secretary, Martin Reynolds, were not as unexpected as Ms. Mirza’s. Critics have faulted Mr. Rosenfeld for his management of Downing Street, while Mr. Reynolds sent an email inviting nearly 100 staff members to a B.Y.O.B. garden party at a time when the government’s own lockdown rules prohibited people from gathering with more than one person outside their families.
The departure of the communications director, Jack Doyle, was also less of a surprise, as his name was linked with some of the parties now under investigation by the police. Critics also faulted him for Downing Street’s steadfast original denials that such gatherings took place and for its insistence that all the Covid rules had been complied with.
Still, the timing of Mr. Doyle’s resignation was unfortunate for Mr. Johnson, heightening the sense of a political unraveling. Yet for all the disarray inside Downing Street, the departures may not have a practical effect on Mr. Johnson’s grip on his job.
He can only be forced out if 54 Conservative lawmakers submit letters calling for a no-confidence vote, and then in that vote, a majority of Tory lawmakers in Parliament cast a ballot against him. The letters are confidential, and the number submitted remains a closely guarded secret.
But on Wednesday, three more Conservative lawmakers openly called on the prime minister to step down, bringing the total who have gone public to around a dozen.