Britain's Prime Minister Boris Johnson reportedly attended a party with staff in the Downing Street garden during the first national lockdown in May last year.
The Guardian and The Independent reported that Mr Johnson was present for 15 minutes at the gathering after a Covid-19 press conference on May 15.
Meanwhile, the Metropolitan Police said it would contact two people who attended a gathering organised by Shaun Bailey’s London mayoral campaign at the Conservative Party headquarters in London on December 14, 2020.
The force said it would investigate reported breaches of coronavirus regulations.
Mr Bailey has apologised “unreservedly” for the event and quit his role chairing the London Assembly’s police and crime committee after pictures of the event were published in the Daily Mirror.
In response to the latest claims about Mr Johnson, Downing Street said he “briefly” met then-health secretary Matt Hancock and his team in the garden, which was “regularly” used for work meetings during summer.
According to the Guardian and Independent’s sources, about 20 staff drank wine and spirits and ate pizza after a media conference in which Mr Hancock told the British public to stay at home “as much as is possible”.
He had also stressed that the rules in force meant “you can meet one other person from outside your household in an outdoor, public place” as long as you kept two metres apart.
Mr Johnson is reported to have told one aide that they deserved a drink for “beating back” coronavirus.
Some aides reportedly carried on drinking into the evening, although there was no suggestion Mr Johnson or Mr Hancock had any alcohol or stayed late.
“In the summer months Downing Street staff regularly use the garden for some meetings," a No 10 spokesman said.
“On May 15, 2020, the prime minister held a series of meetings throughout the afternoon, including briefly with the then-health and care secretary and his team in the garden following a press conference.
“The prime minister went to his residence shortly after 7pm. A small number of staff required to be in work remained in the Downing Street garden for part of the afternoon and evening.”
Hannah Brady, whose father died from the virus the day after the alleged event, said the reports made her sick.
Ms Brady, a spokeswoman for Covid-19 Bereaved Families for Justice, a campaign group of thousands of people bereaved by Covid, said she met Mr Johnson some months later and showed him a photo of her late father in hospital, taken on the day of the reported gathering.
“The prime minister looked me in the eye and told me he’d ‘done everything he could’ to protect my Dad. It’s disgusting,” she said.
Labour’s Fleur Anderson, the shadow paymaster general, said: “It seems that from the very beginning of this awful pandemic the prime minister was setting a culture of disregarding the laws he was applying to the rest of us.
“People have made immense sacrifice during this crisis. It is starting to look like the prime minister has only dithered, partied and eroded public trust.
“As is always the case with Boris Johnson, it’s one rule for him and one rule for the rest of us.”
The claims about May 15 are the latest in a series of accusations about events in Westminster while restrictions on social contact were in force.
Cabinet Secretary Simon Case is investigating gatherings reported to have taken place in Downing Street and the Department for Education in November and December.
Scotland Yard said it would not commence an investigation into those allegations unless new evidence came to light, with Mr Case expected to hand over any material relating to behaviour that could be criminal.
But in relation to the Bailey campaign event, the Met said it was “aware of a gathering at an address in Matthew Parker Street” – the location of Conservative Campaign Headquarters.
“Officers will be making contact with two people who attended in relation to alleged breaches of the Health Protection (Coronavirus, Restrictions) Regulations,” the force said.