The PM says all Covid rules were followed in Downing Street last year – but Labour accuses him of hypocrisy.
Boris Johnson has not denied claims Christmas parties were held in Downing Street last year but insisted no Covid rules were broken.
Labour leader Sir Keir Starmer accused the PM of hypocrisy for flouting the rules he had ordered the rest of the country to follow.
It follows a Mirror newspaper report of drinks parties and quizzes in November and December last year.
The prime minister said “all guidance was followed completely”.
According to the Mirror, the official No 10 staff Christmas party was cancelled last year, but an unofficial party, which the PM did not attend, took place on 18 December.
Aides packed into a room for drinks, a Christmas quiz and a Secret Santa, the newspaper claims.
A Downing Street spokeswoman said they “don’t recognise this report” and “Covid rules have been followed at all times”.
The BBC’s deputy political editor Vicki Young said Downing Street was very reluctant to answer detailed questions about exactly what went on, but they did not deny parties took place.
London was placed under Tier 3 lockdown restrictions on 14 December, after which time it was illegal to mix indoors with anyone outside your household or support bubble.
At Prime Minister’s Questions, Sir Keir said: “Does the prime minister really expect the country to believe that while people were banned from seeing their loved ones at Christmas last year, it was fine for him and his friends to throw a boozy party in Downing Street?”
Mr Johnson said the rules had been followed and took a swipe at Sir Keir’s reported disagreements with Labour’s deputy leader Angela Rayner.
“Can I recommend to (him) that he does the same with his own Christmas party, which is advertised for 15 December, to which unaccountably he’s failed to invite the deputy leader” said the PM.
The SNP’s Westminster leader, Ian Blackford, accused the prime minister of hosting an event that broke lockdown rules.
“The prime minister might be denying it but I’ve spoken to the Mirror newspaper this morning and they are confirming what happened, and they have legal advice on potential illegality,” he said.
“At a time when public health messaging is so vital, how are people possibly expected to trust a prime minister when he thinks it’s one rule for him and one rule for everybody else?”
The prime minister said: “He’s talking total nonsense. I think he would have been better off, frankly, saying something about the victims of storm Arwen in Scotland.”
The prime minister also gave a speech at a “packed leaving do” for an aide on 27 November, when the country was in its second lockdown and socialising was banned, according to the Mirror.
Another party was reportedly held on 13 November, the night the PM’s top aide Dominic Cummings left Downing Street, with Mr Johnson and Cummings ally Lee Cain attending.
Mr Johnson has urged people not to cancel their Christmas parties this year, despite the emergence of the Omicron variant of coronavirus.
The PM has urged people to get a booster jab and follow new, tighter restrictions, with face masks once again being required on public transport and in shops in England.