No 10 staff partied until the early hours of the morning in a seven-hour drinking session on the eve of the Duke of Edinburgh’s funeral, it has been reported.
The Daily Telegraph said it had obtained further details of the two leaving dos on April 16 last year, showing they carried on until 1am.
It came as Scotland Yard were reportedly meeting Tory rebel William Wragg to discuss allegations of threats and blackmail of backbenchers by government whips in another headache for Boris Johnson, The Telegraph said.
A Met spokesman refused to comment on any potential meeting on Friday night, saying only: “As with any such allegations, should a criminal offence be reported to the Met, it would be considered.”
At the party wine and spirits with mixers were said to have been served in disposable plastic cups, and at one point alcohol was reportedly spilled on an office printer.
Takeaway pizzas were reported to have been ordered in and some of the revellers were said to have used a slide belonging to Mr Johnson’s son, Wilfred.
It has previously been reported that Wilfred’s swing was damaged as the two events merged in the Downing Street garden.
Downing Street apologised to Buckingham Palace when the details of the parties first emerged last week, while Mr Johnson – who was not present – said he “deeply and bitterly” regretted what happened.
Labour deputy leader Angela Rayner described the latest reports as “disgusting”.
“Shameful details of ridiculous behaviour, when the British public gave up so much,” she tweeted.
“This is a culture that Boris Johnson set. Rules didn’t apply in his Downing Street. He needs to finally take responsibility.”
Around 30 people were reported to have attended the two parties – one for departing communications director James Slack and the other for a photographer who was leaving.
At the time the country was in a period of national mourning for the duke, while Covid restrictions banned socialising indoors except with members of the same household or support bubble.
The Telegraph said that it had seen a photograph of staff at one of the parties – some with drinks – gathered in the Downing Street basement.
The paper said that it had also seen text messages indicating that they were still carrying on at 1am, having started around 6pm.
The latest report comes as Sue Gray, the senior civil servant investigating lockdown parties in Whitehall, is expected to deliver her report next week.
Mr Johnson has committed to publish her findings and make a statement to the Commons.
Meanwhile Downing Street is resisting opening an investigation into allegations of Tory MPs being blackmailed into supporting Mr Johnson as he faces a threat to his leadership, despite a Cabinet minister saying they need to be looked at.
Business Secretary Kwasi Kwarteng disputed the allegation first made by a senior Conservative, but said if true it would be "completely unacceptable" and ministers "need to get to the bottom of the matter".
But No 10 suggested on Friday that an investigation will only be launched "if there was any evidence" to support the claims, despite calls from Labour and Tory MPs.
William Wragg said critics considering triggering a no-confidence vote in the Prime Minister were receiving threats to "withdraw investments" from constituencies, as well as "intimidation" from No 10 staff.
Mr Wragg, chairman of the Commons Public Administration and Constitutional Affairs Committee, said the threats could amount to "blackmail" and urged colleagues to report them to the police.
Christian Wakeford, the Bury South MP who defected from the Tories to Labour, then said he was threatened that funding for a new school in his constituency would be withheld if he did not vote with the Government over free school meals.
Mr Kwarteng told Sky News: "As far as the specific allegation about whips withholding funds, I think that's completely unacceptable.
"Any form of blackmail and intimidation of that kind simply has no place in British politics.
"We need to get to the bottom of the matter. But I find it very unlikely that these allegations are true."
The Business Secretary said Mr Wakeford's "very serious" allegation has so far been "unsubstantiated".
"I'm sure it will be investigated if it's not being so already - after 12 years as an MP I've never heard anything like this," Mr Kwarteng told BBC Radio 4's Today programme.
"Having been an MP for 12 years I've never heard of anyone making a threat, certainly not to me or to anybody else of that kind, doesn't mean it's not true."
But a spokesman for the Prime Minister said: "We're not aware of any evidence to support what are clearly serious allegations.
"If there was any evidence to support it, it would of course be looked at."
On Thursday, the Prime Minister said Mr Wragg's allegation will "of course" be looked into, but he added he has "seen no evidence" to support it.
The Times reported Tory MPs wanting to oust the Prime Minister are considering publishing a secretly recorded conversation with the chief whip, and messages, to help support the claims.
Douglas Ross, the Scottish Conservative leader who is among those demanding Mr Johnson's resignation, said the allegations should be "properly investigated".
Mr Wragg is one of a handful of Tory backbenchers to have said publicly they have submitted a letter to the chairman of the backbench 1922 Committee, Sir Graham Brady, calling for a no-confidence vote in Mr Johnson's leadership.
Mr Wakeford said he had done the same before he defected to Labour shortly before Prime Minister's Questions this week.
New claims of threats under a previous administration also emerged on Friday when former Tory MP Ben Howlett said an ex-whip warned him funds would be withheld from his constituency over a link road project if he did not support the Government during Brexit votes.
Mr Howlett, the MP for Bath between 2015 and 2017, told the PA news agency: "If I was a less resilient MP, in those days I would've ended up thinking, 'Oh god am I going to carry on rebelling against the Government on Brexit if my major campaign message was going to be undermined as a result', there was some pretty devious tactics."
On the current allegations in Westminster, he said: "As a Prime Minister who's trying to build bridges with his backbenchers it doesn't look very good at all, in fact it's completely counterproductive at this moment in time to end up sending his flunkies to persuade a load of backbench MPs to go and support him by using tactics like that."