Boris Johnson is facing fresh pressure over his leadership after new details emerged of the alleged Tory Christmas party during lockdown last year.
The Daily Mirror reported that the quiz on 15 December – which the prime minister helped to host – had been held virtually, but with many taking part from the offices of Downing Street.
However, No 10 staff who stayed in Downing Street to take part in the quiz were allegedly told to “go out the back”, in a WhatsApp message.
No 10 previously said that Downing Street staff were “often required to be in the office to work on the pandemic response” during the various lockdowns.
And therefore “those who were in the office for work may have attended virtually from their desks”.
But the Mirror said a message sent by No 10’s head of HR on the night advised that those who had stayed behind to take part “go out the back” when they left.
The paper also alleges that team names for the quiz included ‘The 6 Masketeers' and ‘Hands, Face, First Place’.
An image previously published by the Sunday Mirror showed the prime minister flanked by colleagues, one draped in tinsel and another wearing a Santa hat, in the No 10 library.
Watch: PM insists he 'broke no rules' with Christmas quiz
The newspaper quoted a source who said many staff were huddled by computers in their Downing Street offices, conferring on questions and drinking alcohol while the quiz was taking place.
ITV News have also reported that an alarm was accidentally set off in a separate room in Downing Street on the night of the alleged quiz.
Sources told the broadcaster that the alert was triggered at the same time as staff ate cheese and drank wine, while also receiving jokey awards.
The alarm prompted a Metropolitan Police officer to enter the reception at No 10 to check for any security breaches, ITV News added.
The party is said to have taken place when Tier 2 restrictions were in place in London – that stated that there could be no mixing of households indoors, apart from support bubbles, and a maximum of six people outside.
Cabinet secretary Simon Case has been tasked with investigating alleged gatherings or parties held in government buildings during restrictions.
A government spokesperson said: “Given there is an ongoing review, it would be inappropriate to comment while that is ongoing.”
Fresh details about the alleged 15 December party come as as the former Conservative mayoral hopeful Shaun Bailey quit as chairman of the London Assembly’s Police and Crime Committee on Tuesday.
His resignation as chairman of the committee came shortly before The Mirror published a photograph of him and other staff at a party in Conservative headquarters.
The image showed 24 people with drinks, and buffet food laid out.
The Tories previously admitted the party had taken place on 14 December, when London was in Tier 2 restrictions, and said that staff had been disciplined.
Last week, Johnson apologised for the "offence caused" by the alleged Christmas party at Number 10 – but said people should stop focusing on the scandal.
Damning leaked footage emerged which showed the PM's former press secretary Allegra Stratton laughing as she answered mock questions from a colleague about the lockdown-busting Christmas party.
Stratton became the first casualty of the affair when she emotionally stood down after video was leaked.
Watch: Shapps condemns 'disgraceful' Christmas party picture