Downing Street staffers partied late into the night on 16 April 2021, on the eve of Prince Philip's funeral, The Telegraph has reported.
The newspaper claimed it has obtained more details regarding the two No 10 drinking parties, which reportedly carried on until 1 a.m., in a seven-hour booze session. The twin social gatherings purportedly saw wine and spirits served in disposable plastic cups, and at one point alcohol was ostensibly spilled on an office printer.
Labour deputy leader Angela Rayner slammed the report as "disgusting", tweeting about "shameful details of ridiculous behaviour, when the British public gave up so much".
"This is a culture that [Prime Minister] Boris Johnson set. Rules didn't apply in his Downing Street. He needs to finally take responsibility", she added.
The remarks came about a week after Johnson's spokesperson apologised to Buckingham Palace for the 16 April 2021 parties, saying "it's deeply regrettable that this took place at a national mourning".
The spokesperson also referred to the apology earlier made by the PM, who has "recognised No 10 should be held to the highest standards and take responsibility for things we did not get right".
This followed reports that the two leaving parties, including one for James Slack, Johnson's director of communications, were held on 16 April, and that they allegedly kicked off as separate events before merging into one large party later that night.
A significant amount of alcohol was reportedly consumed during the gatherings amid the UK being under step two of a strict coronavirus lockdown plan, which, among other health restrictions, explicitly barred indoor socialising.
Johnson, meanwhile, remains under pressure over the "partygate" row as a group of Tory backbenchers wants to oust him, awaiting the publication of the results of senior civil servant Sue Gray's investigation into a number of COVID lockdown-breaking No 10 parties that were held in 2020 and 2021.