Former minister Tobias Ellwood told Boris to “lead or step aside” in a scathing interview with the BBC.
“We need leadership,” he told the broadcaster in comments likely to heap further pressure on the embattled Prime Minister.
However, fresh revelations published by the Mirror on Friday night revealed that Downing Street staff held “wine-time Fridays” throughout the pandemic.
The regular bash was so popular that staff bought a £142 fridge to keep bottles of white wine and beer cool, the paper added.
Boris Johnson has urged disgruntled Tory MPs to wait until a formal inquiry – led by senior civil servant Sue Gray – is completed before making conclusions.
However, backbencher Andrew Bridgen said he did “not need to see what Sue Gray says to know that, for me, Boris Johnson has lost the moral authority to lead the country”.
The North West Leicestershire MP confirmed he submitted a letter of no confidence in Mr Johnson’s leadership “some time ago”.
Only a handful of Tories have publicly declared they have submitted letters to the 1922 Committee of backbench MPs.
According to the Telegraph, it is estimated that about 20 might have been handed in – far short of the 54 needed to trigger a leadership vote.
Mr Bridgen, asked by BBC Breakfast about reports of “wine time Friday” sessions in Downing Street during lockdown, said: “It doesn’t matter, quite honestly, if the Prime Minister was present or not present.
“Ultimately, he is responsible for what goes on in Government, he is responsible for the culture in No 10, and what we’re seeing is a culture where it is one rule for them and the rest of us do as we’re told, and that’s just not acceptable.
“I’m not sure that any apology is going to put that right.”
Labour leader Sir Keir Starmer says Mr Johnson has lost the “moral authority” to run the country.
He told the Fabian Society conference in London: “The moral authority matters, of course, in relation to Covid, but we’ve got other massive challenges facing this country.
“We’ve got a Prime Minister who is absent – he is literally in hiding at the moment and unable to lead, so that’s why I’ve concluded that he has got to go.
“And of course there is a party vantage in him going, but actually it is now in the national interest that he goes, so it is very important now that the Tory party does what it needs to do and gets rid of him.”
Mr Johnson faced further embarrassment after Downing Street was forced to apologise to Buckingham Palace on Friday after it emerged two staff parties were reportedly held on the eve of the Duke of Edinburgh’s funeral.
Witnesses said alcohol was drunk and guests danced to music as two after-work events merged on April 16 2021, with a person sent to a local shop with a suitcase to buy wine, according to the Telegraph, which first reported the allegations.
Ms Gray is said to have been “completely blindsided” by the latest revelations, the Times reported.
The newspaper said the Cabinet Office official is concerned that Downing Street staff are withholding information about parties from her as she looks to establish the facts.