Pressure is mounting on British Prime Minister Boris Johnson amid fresh allegations that two further Downing Street parties were held while coronavirus restrictions were in place, the night before Prince Philip's funeral.
The events were held in April last year, while the country was in a period of national mourning, it was reported.
Mr Johnson was said to have been away from Downing Street at the time.
Liberal Democrat leader Ed Davey said Queen Elizabeth's lonely appearance at her husband's socially-distanced funeral was the "defining image of lockdown".
"Whilst she mourned, Number 10 partied. Johnson must go," he said.
The news came as Andrew Bridgen, the Conservative MP for North West Leicestershire, was the latest to publicly announce he had submitted a letter of no confidence in the Prime Minister last night.
He was the fifth MP to say he had written to Graham Brady, the chair of the 1922 Committee, calling for a vote on Mr Johnson's future as head of the party.
The Telegraph has reported that as many as 30 letters have been submitted so far. A total of 54 are needed to trigger a vote.
However, in a rare ray of hope for Mr Johnson, it was reported that an inquiry into alleged lockdown-busting events by senior official Sue Gray was expected to find no evidence of criminality.
However The Times reported that the investigation could censure Mr Johnson for a lack of judgement.
The newspaper said Ms Gray was expected to avoid concluding whether the Prime Minister breached the ministerial code, as this would fall outside her remit.
But she is set to criticise the culture in Downing Street, it said.
Ms Gray is examining a series of parties and gatherings held in No 10 and Whitehall in 2020 while coronavirus restrictions were in force.
The new allegations that two Downing Street parties took place the week after Prince Philip's death, and on the eve of his funeral, emerged yesterday evening.
The Telegraph reported that advisers and civil servants gathered after work for two separate events on 16 Apri 2021.
They were to mark the departure of James Slack, Mr Johnson's former director of communications, and one of the his personal photographers, the newspaper said.
The Telegraph cited a No 10 spokesperson as saying Mr Johnson was not in Downing Street that day. He is said to have been at Chequers.
It reported accounts from witnesses who said alcohol was drunk and guests danced to music.
The two events are said to have started separately and later merged.
At the time, UK government guidance stated:
"You must not socialise indoors except with your household or support bubble. You can meet outdoors, including in gardens, in groups of six people or two households."
On Wednesday, Mr Johnson apologised for attending a "bring your own booze" party in the Downing Street garden in May 2020, during the first coronavirus lockdown, but insisted he believed it was a work event and could "technically" have been within the rules.
Cabinet ministers defended Mr Johnson after his apology, but the late interventions of Foreign Secretary Liz Truss and Chancellor Rishi Sunak - both tipped as potential successors - did little to instil confidence in his future.
But Mr Johnson faced open revolt from one wing of his party, as Scottish Conservative leader Douglas Ross urged him to quit, with almost all Tory MSPs supporting the call.