LONDON  — The “partygate” scandal that threatens to derail U.K. Prime Minister Boris Johnson’s administration deepened Tuesday as police opened an investigation into gatherings at government offices that allegedly violated COVID-19 lockdown rules.

London’s Metropolitan Police Service has launched an inquiry into “a number of events” at Johnson’s Downing Street office and other government buildings because they met the force’s criteria for investigating the “most serious and flagrant” breaches of coronavirus rules, Commissioner Cressida Dick told a committee of the London Assembly, the capital’s local government council.

Johnson is facing calls to resign amid revelations that he or his staff attended a series of social events during periods of lockdown when most social gatherings were banned in England, forcing average citizens to miss weddings, funerals and birthdays as friends and relatives died alone in hospitals. The gatherings are already being investigated by a senior civil servant whose report has been anxiously awaited by lawmakers and the public.

“As a result, firstly, of the information provided by the Cabinet Office inquiry team and, secondly, my officers’ own assessment, I can confirm that the Met is now 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,” Dick told the committee.

Britain’s Prime Minister Boris Johnson arrives at 10 Downing Street, in London, Monday, Jan. 24, 2022. AP Photo/Alberto Pezzali

Police have already assessed several other events and determined that they do not meet the threshold for further investigation, the commissioner said. She declined to provide specifics about the gatherings.

The announcement throws into doubt the timetable for when Sue Gray, the civil servant leading the Cabinet Office inquiry, will release her report. Gray had been expected to finish this week, but rules governing the investigation allow the inquiry to be paused if she turns over evidence of potential criminal offenses to the police.

The prime minister’s spokesman, Max Blain, said the investigations team and the police were talking.

“That still needs to be worked through, both in relation to what may or may not be published and the ongoing work of both the police and the (Gray) investigation,” he said.

Even before the police investigation was announced, Johnson was fighting off new allegations of rule breaking aimed directly at him.

ITV News reported late Monday that Johnson’s then-fiancee threw a birthday party for him — complete with cake — inside his Downing Street offices on June 19, 2020, followed by another gathering for family and friends in his official residence.

The prime minister’s office confirmed that the events took place, but denied that they violated lockdown regulations. The first was a brief gathering with colleagues who Johnson was already in close contact with and the second involved a small number of family members who met outside in a garden, in line with coronavirus rules.

Such careful parsing of the rules fueled a debate in the House of Commons, where opposition lawmakers once again called on the prime minister to resign.

Martin Docherty-Hughes of the Scottish National Party argued that the latest gatherings were indeed parties by quoting the late celebrity chef Julia Child, who once said “a party without cake is just a meeting.”

“Johnson’s staffers supplied a cake,” he said. “Ergo, it was a party.”

But Paymaster General Michael Ellis, who represented the government, said cake did not a party make.

“If while at work someone eats cake for 10 minutes, I do not think that conclusions can be drawn from that,” Ellis responded.

The fact that politicians are relying on such technicalities to justify for their actions is “farcical,” said Catherine Haddon, an expert on the constitution at the Institute for Government in London.

“It’s not just about sort of the technicalities of the law, whether there is a sufficient defense or not. It’s about public perception because people were losing their loved ones at this time, you know, unable to to say goodbye to them in person..,” she told The Associated Press.

The police investigation is just the latest episode in the “partygate” scandal that has destabilized Johnson’s conservative government for the past six weeks. Johnson initially denied that any rules had been broken, but he was forced to order an investigation after video emerged of a senior staff member making jokes about a wine-and-cheese party in the prime minister’s press office.

Johnson later apologized for attending a party in the garden outside his Downing Street offices in May 2020, saying he initially thought it was a work gathering allowed by the rules but recognized on hindsight that it wasn’t appropriate.

Police have previously faced criticism for suggesting they wouldn’t investigate the Downing Street parties because officers don’t routinely investigate historical breaches of coronavirus regulations, where the only penalty available is a fine. Fines of up to 10,000 pounds ($13,490) were imposed for breaching lockdown rules.

But Dick said Tuesday that police were prepared to conduct retrospective investigations where there were “really flagrant breaches” of the rules. Before such investigations are carried out, she said, three criteria must be met: there is evidence that those involved knew or should have known they were breaking the law, not investigating would “significantly undermine” the law, and there seems to be no reasonable defense for the conduct.

“So in those cases, where those criteria were met, the guidelines suggested that we should potentially investigate further and end up giving people tickets,” she said.