One Conservative challenged Mr Johnson during a meeting of the 1922 Committee of backbenchers on whether he would impose a prohibition after the senior civil servant’s report.
Ms Gray described officials drinking so heavily they were sick, became involved in altercations and abused security and cleaning staff.
A source in the room said: “He made the point he’s not a big drinker himself but had alcohol been banned in 1940 we might not have won the Second World War.”
The Tory party source argued it would be wrong to ban alcohol at events with foreign dignitaries, charities and other guests who attend Downing Street.
But he added: “There’s recognition that part of decompressing at the end of a long day involves having a drink but not checking out at 4am absolutely legless, having been rude to a member of staff, having thrown up over a sofa.”
Ms Gray’s inquiry also detailed how staff carried on drinking in No 10 until the early hours at parties on the eve of the Duke of Edinburgh’s funeral, with the last person not leaving until 4.20am.
But the source insisted Mr Johnson had been keen to emphasise that No 10 was not like a “Saturday night in July in Ibiza”, and staff were working hard on the pandemic response.