London’s Metropolitan Police announced an initial 20 fines last month, without disclosing the number or identities of those being fined.
The announcements have revived the so-called “Partygate” scandal, which left Johnson fighting for political survival after a number of lawmakers from his ruling Conservative Party withdrew their support for his leadership.
Johnson’s spokesman said after the first fines were issued that the UK leader was not among those hit, although opposition politicians reiterated their calls for his resignation.
The London force is investigating claims that Johnson and government officials organised and attended at least a dozen boozy events in 2020 and 2021 that violated Britain’s then-strict virus curbs.
“The investigation into allegations of breaches of Covid-19 regulations in Whitehall and Downing Street continues to progress,” the Met said in a statement.
“As of today, 12 April 2022, we have made over 50 referrals for fixed penalty notices … for breaches of Covid-19 regulations,” it said.
“We are making every effort to progress this investigation at speed, this includes continuing to assess significant amounts of investigative material,” it added.
Johnson has already apologised for the parties, which included Christmas celebrations and a drink-fuelled gathering the evening before Prince Philip’s funeral.
The prime minister, who initially denied any rule-breaking events had occurred in the complex where he lives and works, has consistently rejected personal wrongdoing.
But the 57-year-old faces a fine unless he can adequately explain why he appeared to attend some social gatherings when his government was telling the public that they were illegal.
His office confirmed in February that Johnson had submitted his response to a police questionnaire on the matter, but sources have said he has not been interviewed in person by investigating officers.
Russia’s invasion of Ukraine has eased the political pressure on Johnson, with the international crisis replacing “Partygate” in the daily headlines.