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”.
Groups were banned from meeting socially outdoors in England on the day the party is alleged to have taken place.
The latest revelations have led to fresh calls for the Prime Minister to be questioned as part of the internal inquiry into a series of parties in Downing Street.
The Met Police 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.”
This is what local residents have said about news of a Downing Street party:
John Richard Hinchliff said: “Does anyone seriously expect this enquiry by their paid servants into themselves to reveal one ounce of truth in it. Also, it has to bring into question do any of the rules and regulations forced on us have any necessary effect whatsoever as to the people in charge of issuing them all chose to totally ignore them and still do.”
Craig Stevenson said: “How hard is this to investigate? The police are stationed inside and outside number 10. They know who comes, who leaves and at what times. The place is covered with CCTV.”
Dorothy Davis, aged 66, said: “If it’s true that it was a party, I think it is shameful and unbelievably disrespectful to the rest of the country. Boris is in a very difficult position, and I think he needs to reconsider how he behaves. I can’t see him resigning, but I’m not very happy with his behaviour at all.”