The police force confirmed it was liaising with the Cabinet Office over the latest claims which are said to have taken place on May 20 2020.
A spokesman for Scotland Yard said: “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.”
ITV News reported that Martin Reynolds, the Prime Minister’s principal private secretary, sent an email to 100 Downing Street employees asking them to “bring your own booze” for an evening gathering.
In an email obtained by the broadcaster, Mr Reynolds said they should “make the most of the lovely weather”.
England was under tough coronavirus restrictions when the message was sent, with groups banned from meeting socially outdoors.
Did the Prime Minister attend the Downing Street party?
The Conservative Party leader sidestepped questions on Monday about whether he attended the evening gathering allegedly organised by Mr Reynolds.
However, multiple reports have suggested the Prime Minister attended the event with his wife, Carrie Johnson.
A No 10 spokesman refused to be drawn on those reports that Mr Johnson had attended the event.
“There is an independent process going on to look into this, led by Sue Gray, and I can’t comment further while that is taking place,” he said.
Ms Gray will look into the numerous claims of rule-breaking events being held in Downing Street during the coronavirus pandemic.
She will look into the May 20 2020 claims and her inquiry will also investigate the garden gathering that took place five days earlier.
What coronavirus rules were in place when the party took place?
Groups were banned from meeting socially outdoors in England on the day the party is alleged to have taken place.
The Metropolitan Police tweeted on the day of the alleged “bring your own booze” event that people could have a picnic, exercise or do sport outside - providing you are “on your own, with people you live with, or just you and one other person”.
Oliver Dowden, the-then culture secretary, used a Downing Street press conference that day to remind the public they could “meet one person outside of your household in an outdoor, public place provided that you stay two metres apart”.
‘It is disgraceful and he should be ashamed’
Labour deputy leader Angela Rayner told ITV News: “It is terrible and I think many people that see the evidence now will not only think that Boris Johnson’s lies are catching up with him, but will see it as absolutely despicable that when they were actually told to follow the rules, Boris Johnson and No 10 were breaking the rules.
“It is disgraceful and he should be ashamed.”
The Liberal Democrats said if rules were found to be broken then “those responsible should face the full force of the law”.
The party’s home affairs spokesperson Alistair Carmichael said: “This garden party looks like a clear breach of lockdown rules at a time the public were being ordered to stay at home.
“Boris Johnson himself said just days after this party that the police should step in to stop people holding outdoor gatherings.
“It would absolutely reek of double standards if the police don’t investigate these allegations in full.”
A version of this article originally appeared on NationalWorld.com