The Met Police has signalled it could now investigate a Downing Street Christmas quiz after a photo of the event emerged.
Hosted by Boris Johnson, the event was one of four Scotland Yard looked at without launching a full investigation, reports the Mirror.
The image shows the Prime Minister flanked by three members of staff, one wearing tinsel and another a Santa hat, and an open bottle of bubbly at a 'virtual' Christmas quiz on December 15, 2020.
At the time London was under Tier 2 regulations banning any social mixing between two or more people from different households.
The Metropolitan Police said in a statement: “The MPs previously assessed this event and determined that on the basis of the evidence available at that time, it did not meet the threshold for criminal investigation.
"That assessment is now being reviewed.”
Barrister Adam Wagner told The Mirror: "The previous photograph of the Prime Minister showed what could have been a meeting briefly interrupted by a Zoom call.
"However, the new photograph shows four people with alcohol and food, as well as a Christmas hat and tinsel, which suggests a Christmas party.
"This was held at a time when indoor social gatherings of two or more people were banned and the Government had told people they "must" not have a Christmas party."
Labour MP Fabian Hamilton raised the photo at today's PMQs, saying: “At the height of the lockdown restrictions in 2020, my constituent, who has worked for the NHS for over 30 years, was diagnosed with a tumour on her spine.
“While she was in hospital undergoing painful surgery, her family obeyed the rules and did not visit her. In the last few minutes, a photo has emerged of the Prime Minister in Downing Street, on 15 December 2020, surrounded by alcohol, food and people wearing tinsel. It looks a lot like one of the Christmas parties that he told us never happened.
“For the sake of my constituent and the sacrifices she made, will the Prime Minister be referring that party to the police, as it is not one of those already being investigated?”
The PM hit back, saying: "He is completely in error."
But Labour MP Gerald Jones said: “The photograph referred to is all over social media; everybody can see the photo; the Prime Minister is in the photo.
“Can I ask him again, will he refer the matter to the police, because it is not one of the parties that are already being investigated by the Metropolitan police?”
Mr Johnson said: “That is precisely the point - it already has been. That event already has been submitted for investigation.”
