Boris Johnson allegedly joked at a boozy No 10 leaving do during the coronavirus pandemic that staff were at “the most unsocially distanced party in the UK”.

The claims will put the former prime minister under further pressure as he faces a parliamentary investigation into whether he misled MPs over the so-called partygate scandal.

A spokesman for Mr Johnson did not deny the comment but insisted the then-PM had “worked constantly” to ensure the Government did all it could to save lives and protect livelihoods during the pandemic.

ITV News reported that the comments were made as staff gathered around a table filled with alcohol and party snacks to hear him toast his outgoing director of communications, Lee Cain, in November 2020.

At the time of the event, England was covered by a second national lockdown with indoor gatherings banned except for in certain circumstances such as for “work purposes”, and social distancing remained the rule in workplaces.

In her report into the partygate row, senior official Sue Gray said she was told the the event on November 13 2020 was not pre-planned but occurred at around the time that “wine time Friday” events in No 10 routinely took place.

Mr Johnson gave a leaving speech for Mr Cain and wine was provided for those attending, Ms Gray’s report said.

The comment made by Mr Johnson is part of a number of new allegations made in an ITV podcast, Partygate: The Inside Story.

It reports that a source said: “I was working late – some music came on, the mumbling sort of rose, and there were loads of people stood around, but this time I came out because I heard the prime minister speaking and that’s when I heard the quote: ‘This is the most unsocially distanced party in the UK right now’ and everyone was laughing about it.”

Mr Johnson was fined as part of a police investigation into gatherings held in Downing Street while social distancing restrictions were in place.

However, he was fined for attending his own birthday party in the Cabinet Room in Downing Street in June 2020 rather than for the alleged party the ITV source mentions.

He is still due to appear before the Commons Privileges Committee over comments he made to MPs from the despatch box about partygate, insisting that he believed rules were followed in No 10.

A spokesman for Mr Johnson said: “During the Covid-19 pandemic Boris Johnson led our country through its most dangerous peacetime crisis in living memory.

“As prime minister during a 24/7 national emergency he worked constantly to ensure the government did everything possible in its power to save lives and protect livelihoods.

“Mr Johnson pays heartfelt tribute to the heroic frontline workers who battled the pandemic, many of whom lost their lives.

“Their service to our country will always be remembered.

“He is also incredibly grateful for the efforts of hardworking staff who were working in central government – the vast majority of them civil servants – who helped co-ordinate the UK’s national response from 10 Downing Street, across Whitehall and throughout the wider UK government.

“Their work was crucial as they helped marshal the UK Government’s response during a national emergency.”

Deputy Labour leader Angela Rayner said: “”As the disgraced former prime minister plots his comeback, he reminds us all yet again why he’s totally unfit for office.

“While people were unable to say goodbye to loved ones or mourn with their families, he was breaking his own rules with reckless abandon and then lying to the British people.

“Conservative MPs were complicit while Rishi Sunak personally propped him up for months as he set about degrading standards in public life. This joke’s not funny any more.”

Liberal Democrat chief whip Wendy Chamberlain said: “These shocking revelations confirm Boris Johnson’s total disregard for the rules he asked us all to follow. He laughed and partied while the rest of the country suffered.

“Conservative MPs should be ashamed that they backed Johnson for so long and that some are even considering putting him back in No 10.

“Rishi Sunak must agree to give evidence under oath to the partygate inquiry about everything he knows about rule-breaking in No 10, including reports that files were shredded. After all their sacrifices, the British people deserve the truth, not more lies and cover-ups.”

Among other claims, ITV reports that whistleblowers told the podcast that staff “corroborated their stories” before filling out Metropolitan Police questionnaires about their potential involvement in rule-breaking gatherings.

The report also suggests a No 10 party on the eve of the Duke of Edinburgh’s funeral service in April 2021 was even more debaucherous than previously documented, with at least two couples “getting it on with each other” and “touching each other up” and two other members of staff “all over each other” in a kitchen area.

The podcast also reports that only half of the parties that occurred were ever investigated by Ms Gray, the senior Cabinet Office official who probed the partygate claims, or the Met.