The image, published by the Daily Mirror, was reportedly taken on December 15, 2020.
At the time, London was under Tier 2 regulations - meaning that any social mixing between two or more people from different households was banned.
The picture shows the Prime Minister next to three members of staff, with one wearing a Santa hat and another some tinsel.
An open bottle of bubbly and half-eaten packet of crisps is on a desk in front of them.
Mr Johnson’s former chief adviser, Dominic Cummings, reacted to the latest image by tweeting: “there’s waaaaay better pics than that floating around, incl in the flat.”
What Boris Johnson said about the new image
Asked about the image during Prime Minister’s Questions by Labour’s Fabian Hamilton, the Prime Minister said it was “completely in error” to describe an image of him at a Christmas quiz as being a party.
Mr Hamilton said: “In the last few minutes a photo has emerged of the Prime Minister in Downing Street on December 15, 2020 surrounded by alcohol, food and people wearing tinsel.
“It looks a lot like one of the Christmas parties he told us never happened.”
He added: “Will the Prime Minister be referring this party to the police as it is not one of the ones currently being investigated?”
Mr Johnson said: “In what he has just said, I’m afraid he is completely in error.”
Challenged again during PMQs, Mr Johnson added: “That event already has been submitted for investigation”.
What happened at the Number 10 ‘virtual’ Christmas quiz?
A Downing Street spokesperson previously confirmed that the Prime Minister had “briefly” taken part “virtually” in the quiz.
It was reported that he surprised staff by turning up on screen as quiz master for one round lasting between 10 and 15 minutes.
A No 10 spokeswoman said: “This was a virtual quiz.
“Downing Street staff were often required to be in the office to work on the pandemic response so those who were in the office for work may have attended virtually from their desks.
“The Prime Minister briefly took part virtually in a quiz to thank staff for their hard work throughout the year.”
The quiz on December 15 took place just three days before an alleged rule-breaking Christmas party in No 10.
Is this event being investigated by the Met Police?
The Met Police are investigating alleged rule-breaking gatherings at 12 events in Downing Street and Whitehall during the pandemic.
However, the Christmas quiz on December 15, 2020 - when this picture was taken - is not one of those events currently being looked at by the force.
However, police have now confirmed that they are reviewing their decision to not include this gathering as part of their investigation.
In a statement, Metropolitan Police said: “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.”
What was the Covid guidance at the time?
London was under Tier 2 restrictions at the time, which prohibited social mixing between different households indoors.
Official guidance said: “Although there are exemptions for work purposes, you must not have a work Christmas lunch or party, where that is a primarily social activity and is not otherwise permitted by the rules in your tier.”
A message from the editor:
Thank you for reading. NationalWorld is a new national news brand, produced by a team of journalists, editors, video producers and designers who live and work across the UK. Find out more about who’s who in the team, and our editorial values. We want to start a community among our readers, so please follow us on Facebook, Twitter and Instagram, and keep the conversation going.