The former PM told a BBC documentary he made contact with royal officials in 2014, suggesting the Queen could “raise an eyebrow” in the close-fought Scottish independence campaign.
A few days before the referendum in September 2014, the Queen told a well-wisher in Aberdeenshire that she hoped “people would think very carefully about the future”.
In an attempt to play down the row over his revelation, Cameron this week insisted he did not ask the Queen to do “anything improper” during the referendum on Scottish independence.
Cameron sought support from the Queen after a poll predicting a Yes victory “panicked” him.
The former prime minister – who has been carrying out a media blitz to promote his memoirs – told BBC Radio 4’s Today programme: “I never asked for anything improper to be said or done.”
He added: “I don’t want to say anything more about this, I’m sure some people would think – possibly even me – that I have already said perhaps a little bit too much.”
But the BBC has now quoted an unnamed source as saying Cameron’s remarks had caused a certain amount of “displeasure” in Buckingham Palace.
The source said that “it serves no one’s interests” for conversations between the prime minister and the Queen to be made public, and “it makes it very hard for the relationship to thrive.”
Cameron had previously told the BBC: “I remember conversations I had with my private secretary and he had with the Queen’s private secretary and I had with the Queen’s private secretary, not asking for anything that would be in any way improper or unconstitutional, but just a raising of the eyebrow, even, you know, a quarter of an inch, we thought would make a difference.”
The Queen’s dealings with the current prime minister are also in the spotlight after Boris Johnson told her to order the suspension of parliament – which is the subject of a legal battle at the Supreme Court.
Cameron has a history of indiscretion in his dealings with the monarch.
He admitted that talking about how she had “purred down the line” to him after the No victory in the Scottish referendum had been a “terrible mistake”.