Mr Johnson is also said to have spoken at two more leaving dos which are also the subject of Scotland Yard inquiries.
It comes as Mr Cummings claimed that “incriminating” photos of the Tory leader at alleged gatherings have been handed to the police.
Here we take a look at what the latest ‘partygate’ allegations are.
What are the latest ‘partygate’ allegations against Boris Johnson?
On the night of Mr Cummings’ departure from No 10 - on November 13 2020 - Mr Johnson was reportedly seen heading up to his flat where a gathering took place.
It was previously reported that aides heard Abba songs blaring from the flat.
On Monday (31 January), the Prime Minister repeatedly refused to say if he was there.
However, Mr Cummings said in an online question and answer session that it was clear there was a party going on and he accused Mr Johnson of lying.
“I’ve talked to people who were in No 10 on 13/11 who could hear the party in No 10 after I’d left – the press office is below the flat,” he said.
“If cops talk to people there that night, there’ll be witnesses who say ‘we could all hear a party with Abba playing’.”
The Prime Minister was also reported to have attended a gathering on December 17 2020 for an official who was leaving.
Mr Johnson reportedly gave a speech for Captain Steve Higham - who was then one of the Prime Minister’s private secretaries, advising on defence and national security issues.
Both the Telegraph and the Guardian also report that he was said to have been present at a leaving do for two No 10 private secretaries on January 14 2021.
One of the officials was said to be a senior policy adviser who was moving to the Department for Digital, Culture, Media and Sport.
Guests were said to have drunk prosecco while Mr Johnson gave a speech thanking the official for their work.
The two papers also said that another event under investigation in the Cabinet Office on June 18 2020 was for Hannah Young, a senior official who was leaving No 10 to become deputy consul general in New York.
What has Downing Street’s reaction been to the latest ‘partygate’ allegations?
Downing Street said it could not comment on the latest reports due to the ongoing police investigation.
What other reaction has there been to the latest ‘partygate’ allegations?
Sir Charles Walker, the vice chairman of the Tory backbench 1922 Committee, became the latest senior figure to call on the Prime Minister to consider his position.
He told Channel 4 News: “I think there’s so much grief and pain out there that if he was to say, ‘Look, I understand that I asked so much of the country and it needs to come to terms with that grief and pain and start the process of healing and if it could do that better without me in Number 10 then I shall stand aside’, that would show great courage on behalf of the Prime Minister.
“I would applaud him for doing that, but that is his decision.”
Tory backbencher, Peter Aldous, the MP for Waveney, said he had submitted a letter to the chairman of the 1922 Committee, and called for a no-confidence vote in Mr Johnson.
However Communities Secretary Michael Gove supported the Prime Minister, saying this was not the time for a leadership contest.
“There’s not going to be a leadership contest. We don’t want one, we don’t need one,” he told the BBC.
What is the latest from Boris Johnson on the Sue Gray report?
The Prime Minister committed to publishing “everything that we can” from the full Sue Gray inquiry.
Asked at a press conference in Kyiv, Ukraine, whether he would commit to publishing the full inquiry, including the 300-plus images handed to investigators, the Prime Minister said: “Yes, of course we’ll publish everything that we can as soon as the process has been completed, as I said yesterday.”
There had been confusion over the extent of what would be published from Ms Gray’s full report.
Mr Johnson refused to accept the demands of Tory MPs and Labour leader Sir Keir Starmer to publish the report in full during a Commons statement.
However, he has now said that a fuller publication of the senior civil servant’s investigation will be published once the Metropolitan Police probe has concluded.
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