The PM today failed three times to deny the events took place last November and December, as one attendee alleged revellers at an unofficial No10 Christmas bash enjoyed food, drinks and games which went on well past midnight.
And a Downing Street insider claimed there were often get-togethers in the evenings while millions of people across the land were observing the strict curbs brought in by Mr Johnson.
The source said: “It was the only place you could get together and socialise. They happened most Fridays.”
The PM was said to have given a speech at a packed leaving do for a top aide on November 27, at the height of the second national lockdown.
And on December 18, it was claimed members of Mr Johnson’s top team held a festive party in Downing Street, with London in Tier 3. The next day he announced Christmas was cancelled.
The Covid-19 Bereaved Families for Justice group slammed the PM, who faced demands to apologise for what appears to be a clear breach of his own rules.
Member Safiah Ngah lost her father Zahari, 68, to the virus in February.
The 29-year-old said: “Last Christmas is sadly one I will never forget.
“One in 20 people in my borough had Covid-19 and my family were desperately trying to do what we could to keep each other safe.
“Unfortunately it wasn’t enough. To think that just a few miles away, Boris Johnson was throwing a ‘Christmas party’, with no care for the rules he had set, is sickening.
“In September, he looked bereaved families in the eye and told them he had done ‘everything he could to keep their loved ones safe’.
“How exactly did breaking the rules himself fit into that?
“While he was enjoying an illegal Christmas party, the people he should have been protecting were dying all around the country.”
“The first thing the Prime Minister must do is acknowledge the hurt this has caused, and apologise.”
Sources claimed at the No10 Christmas party officials glugged down bottles of wine and beer and had a Secret Santa and a festive quiz.
Around “40 or 50” people were said to have been crammed “cheek by jowl” into a medium-sized room in No 10 for both of the events.
Mr Johnson was grilled by Kier Starmer over the parties. He insisted the rules were followed at all times.
The Labour leader asked the PM: “As millions of people were locked down last year, was a Christmas party thrown in Downing Street for dozens of people on December 18?”
A squirming Mr Johnson replied: “All guidance was followed completely.”
Mr Starmer said: “The defence seems to be ‘no rules were broken’.
“Well, I’ve got the rules that were in place at the time of this party, they are very clear.
“You must not have a work Christmas lunch or party.
“Does the Prime Minister really expect the country to believe that while people were banned from seeing their loved ones at Christmas, it was fine for him and his friends to thrown a boozy party?
“The Prime Minister does not deny there was a Downing Street Christmas party last year.
“He says no rules were broken. Both of those things can’t be true.
“He is taking the British public for fools.”
Shadow Foreign Secretary David Lammy added: “With this government, it’s one rule for them and another rule for everybody else.”