The Metropolitan Police has said it does not routinely probe "retrospective breaches" of Covid laws amid calls for an investigation of a No 10 Christmas party held during 2020's restrictions.
The party took place on 18 December, with a source telling the BBC that "several dozen" people attended.
However, Covid restrictions in place at the time banned such events.
The PM, who was not at the party, said no Covid rules were broken but No 10 has not said how party-goers complied.
And Deputy Prime Minister Dominic Raab told BBC One's Andrew Marr Show that media reports of events were "unsubstantiated" as they had come from anonymous sources.
But he added: "If anyone held a party that it is contrary to the rules, of course that is the wrong thing to do."
A source who attended the event told the BBC party games were played, food and drink were served, and the party went on past midnight.
The Mirror newspaper, which was the first to report the claims, also said Boris Johnson 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.
Writing separately to Met Police Commissioner Dame Cressida Dick on Friday, Labour MPs Neil Coyle and Barry Gardiner called for a full investigation into whether or not any laws had been broken.
Sharing his letter on Twitter, Mr Coyle, the MP for Bermondsey and Southwark, in south London, said from reading the guidance, he believed "holding these events was a breach of the rules at the time".
He said: "Like most constituents, I followed the rules and did not see my own dad last Christmas and, sadly, it was to be his last.
"The sense of outrage from constituents is palpable that they followed the rules whilst those responsible for devising and enforcing them were breaching them at the top of government."
His comments were criticised by Conservative MP Lucy Allan, who said: "Is this what you were sent to Parliament to do? Is this what you want the police to spend time doing?"
Also sharing his correspondence on Twitter, Mr Gardiner, the MP for Brent North, in north-west London, said: "I hope you agree that no-one is above the law and your service needs to maintain public confidence that Covid rules apply equally to all people."
He added he was "surprised" to hear Dame Cressida tell LBC the force was not currently investigating the party.
In a statement, the UK's largest police force said it was "aware of widespread reporting" of "alleged breaches of the Health Protection Regulations" at a government building on two dates in November and December.
The Met added it was the force's "policy not to routinely investigate retrospective breaches" of Covid laws but said it would "consider" the letters it had received.
Two days prior to the event, London was plunged into Tier 3 lockdown restrictions, which banned people from mixing indoors with anyone not in their household or support bubble.
People were allowed to gather if it was reasonably necessary for work purposes but that would not have included holding a party.
Labour's deputy leader, Angela Rayner, wrote to Cabinet Secretary Simon Case on Thursday, saying she found it "difficult to understand" how either event could have complied with the rules.
She asked Mr Case if he would conduct an inquiry into the events and if he would refer any potential breach of the Covid regulations by Mr Johnson to the Met Police.
Boris Johnson has faced sharp criticism over the party with Labour leader Sir Keir Starmer saying it showed it was "one rule for them and another rule for everybody else" and that it sent "completely the wrong message" to the public.
Families who lost loved ones during the pandemic said they were "sickened" by the reports, with the Covid-19 Bereaved Families for Justice group calling for an apology from Mr Johnson.
Asked by reporters on Thursday why he would not tell the public what happened at the party, the prime minister replied: "Because I have told you."
Instead, Mr Johnson tried to focus on this Christmas, saying the government was taking a "balanced and proportionate approach to the risk" and "people shouldn't be cancelling things", such as parties and nativity plays, because of concerns about the Omicron variant.
In a statement, the Met said: "The Metropolitan Police Service is aware of widespread reporting and has received correspondence relating to alleged breaches of the Health Protection Regulations at a Government building on two dates in November and December 2020.
"It is our policy not to routinely investigate retrospective breaches of the Covid 19 regulations, we will however consider the correspondence received."
- WHAT RISK DOES AI POSE TO OUR FUTURE?: Stuart Russell explores the future of Artificial Intelligence
- THE FAMOUS PHOTO OF A US PRESIDENT THAT'S ACTUALLY FAKE: How long has catfishing been around for?