While meeting in New York, Mr Cameron was overheard telling Mr Bloomberg that the Queen practically “purred down the line” when he had called her to say that Scotland had voted no to independence.
The comments were accidentally picked up by a Sky News crew as the PM walked through a business leaders meeting.
Throughout the eavesdropped conversation Mr Cameron was apparently expressing his anxiety about the Scottish referendum and confiding in Mr Bloomberg about the “relief” he felt when the ‘no’ vote trumped independence.
“The definition of relief is being the prime minister of the United Kingdom and ringing the Queen and saying, ‘It’s alright, it’s OK’. That was something,” Mr Cameron said.
“She purred down the line.”
After a few seconds of inaudible recording, Mr Cameron also added: “But it should never have been that close.”
“It wasn’t in the end, but there was a time in the middle of the campaign when it felt…”
Mr Cameron’s indiscreet remarks also included a mischievous suggestion of taking legal action against the pollsters pitting the campaign as neck and neck.
“I’ve said I want to find these polling companies and I want to sue them for my stomach ulcers because of what they put me through,” Cameron said.
“It was very nervous moments.”
During the liberation campaign the Queen publicly remained impartial but Mr Cameron’s revelations suggest she was more than delighted when the Scots voted 55 per cent to 45 per cent in favour of remaining part of the United Kingdom.
Downing Street has so far taken no official position on the embarrassing gaffe but some royalists appear to be trying to pressure Mr Cameron to make a formal apology to the Queen.
“Some will say this is incredibly indiscreet, and that conversations he has with the Queen shouldn’t be passed on no matter who you are,” Royal Correspondent, Paul Harrison told Sky News.
After the incident a palace spokesperson told the UK’s Express it “wouldn’t comment on private conversation between the Queen and the Prime Minister.”