Britain s Prime Minister Boris Johnson (2ndR) walks with corporal Lorna MacDonald during a visit to a vaccination centre in Northampton on January 6, 2022. AFP
In the latest in a string of such allegations, Johnson and others allegedly held a drinks gathering in the garden of his official residence in May 2020 when any in-person socialising was outlawed.
An email leaked late Monday indicated that Martin Reynolds, a senior civil servant, invited more than 100 Downing Street colleagues to "bring your own booze" to the event, which Johnson and his wife Carrie allegedly attended.
The potentially highly damaging revelations follow a series of similar accusations which emerged last month about Downing Street parties held during later lockdowns in the run-up to Christmas in 2020.
They prompted Johnson to appoint another senior civil servant, Sue Gray, to investigate the allegations, and she is now expected to expand her probe to cover the new claims.
Meanwhile in a statement released late Monday, London police said they were also making enquiries over potential breaches of the lockdown laws in relation to the May gathering.
"The Metropolitan Police Service is aware of widespread reporting relating to alleged breaches of the Health Protection Regulations at Downing Street on May 20 2020 and is in contact with the Cabinet Office," the force said.
Johnson has previously denied knowledge that any rules were broken in Downing Street during the pandemic, as he faced weeks of excoriating headlines over the previous allegations before Christmas.
But the latest accusations appear to directly contradict those claims.
In the May 2020 email sent by Reynolds, he wrote: "After what has been an incredibly busy period it would be nice to make the most of the lovely weather and have some socially distanced drinks in the No10 garden this evening."
Britain at the time was in the throes of its first lockdown, and outdoor social gatherings of any kind were banned.
ITV News, which obtained the email, said around 40 staff ended up gathering in the garden that evening, eating picnic food and drinking.
BBC News, which followed up, said it had contemporaneous emails from some Downing Staff that questioned the wisdom of the invitation.
"It's right that Sue Gray is looking into this matter independently," Health minister Ed Argar told Sky News on Tuesday during a round of broadcast interviews.
"I'm not going to make comments that would prejudge or get in the way of that."
Johnson had hoped to start the new year with a reset of his embattled government, leaving behind the so-called "partygate" scandals that ratcheted up the pressure on his position, after a series of other claims of sleaze.
But many of Tuesday's newspapers, including those which normally back Johnson and his Conservative party, again splashed the latest revelations over their front pages.
"Enough Boris! You must end 'partygate' farce now" implored the typically supportive Daily Express.