U.K. Police Say They Are Investigating Downing Street Lockdown Parties

LONDON — The British police have opened an investigation into parties held at 10 Downing Street and other government offices during the coronavirus lockdown, an ominous development for Prime Minister Boris Johnson, who is trying to hold off a career-threatening challenge to his leadership over his handling of the scandal.

The commissioner of the Metropolitan Police, Cressida Dick, confirmed on Tuesday that the police are investigating “a number of events that took place at Downing Street and Whitehall in the last two years in relation to potential breaches of Covid-19 regulations.” She declined to give further details.

The disclosure could delay publication of the most serious findings of another crucial investigation, which is being led by a senior civil servant, Sue Gray. Mr. Johnson has appealed to Conservative lawmakers and the public to withhold judgment until the release of that report.

Officials had earlier said they expected Ms. Gray’s report to be released in coming days, but a police investigation may push back its release by days or even potentially weeks. That would hamper Mr. Johnson’s efforts to put the scandal behind him. Ms. Dick said the police investigation was opened as a result of information turned over by Ms. Gray’s inquiry.

The steady drip of disclosures about social gatherings — most recently news that Mr. Johnson’s wife, Carrie Johnson, and staff members threw him a surprise birthday party in June 2020, when such gatherings were forbidden — has seriously damaged the prime minister’s position. Police officers who guard the Downing Street complex are in a particularly good position to monitor the comings and goings of staff members.

An unknown number of Conservative lawmakers have submitted confidential letters calling for a vote of confidence in the prime minister. If the number of letters exceeds 54, Mr. Johnson would face such a vote, which analysts said would cripple his leadership even if he manages to win a majority of the votes.

Mr. Johnson’s office said Tuesday that Ms. Gray would pause work on any of the events being investigated by the police. She will continue to conduct her inquiries into gatherings that were not judged serious enough for the police to look into, and could make those findings public before they have completed their inquiries, it said.

“I welcome the Met’s decision to conduct its own investigation because I believe this will help to give the public the clarity it needs and help to draw a line under matters,” Mr. Johnson said in Parliament on Tuesday.

His official spokesman said that the prime minister did not believe he had broken the law. No mention of the police investigation was made during a cabinet meeting on Tuesday morning, although Mr. Johnson was informed about it before the meeting.

While the latest development could give Mr. Johnson space to breathe as the police investigation unfolds, it banishes any hope that Ms. Gray’s investigations would clear Downing Street of misbehavior and allow it to quickly move beyond the scandal.

Were Mr. Johnson to be questioned himself by police, it would not be the first time for a prime minister in recent decades. In 2006 and 2007, toward the end of his tenure as prime minister, Tony Blair was questioned twice by police over allegations that honors had been given to business leaders in exchange for donations.

However, the crisis over parties in Downing Street, which has dominated the news, now looks likely to paralyze the government and hit the Conservative Party in the polls.

The main question for Mr. Johnson now is whether his own lawmakers are willing to wait for the outcome of the police investigation, or whether the latest twist will prompt enough of them to write formal letters of protest to trigger a motion of no-confidence in him.

On Tuesday one Conservative member of Parliament, Michael Fabricant, wrote on Twitter that he was pleased by the development. “Rather better to have a professional investigation than trial by social and mainstream media!” he said.