DAVID Cameron has claimed his "frustration" with Alex Salmond during the 2014 Scottish independence referendum campaign prompted his controversial plea for the Queen to intervene but admitted he now wanted to avoid making his indiscretion "worse".

Buckingham Palace made clear its “displeasure” at the former Prime Minister’s revelation that he had asked Her Majesty to “raise an eyebrow” at the prospect of an independent Scotland.

A senior source made clear "it serves no one's interests" for conversations between the PM and the head of state to be made public, stressing: “It makes it very hard for the relationship to thrive."

But Mr Cameron’s request had the desired effect as days later the Queen urged Scots to “think very carefully” about their future; interpreted widely as her urging voters to stick with the Union.

The former Conservative leader expressed his “delight” at Her Majesty’s intervention, saying later her comments "helped to put a slightly different perception" on the campaign.

In an interview with Sky News' Sophy Ridge on Sunday, Mr Cameron acknowledged his revelations, made in a BBC documentary, had caused consternation but defended his decision, saying the suggestion he had revealed details of a private conversation with the monarch was not "correct".

He explained: "What I have said in that programme, and I don't want to add to it in any way, was about conversations between my aides and her aides, actually."

Emphasising the political context, the ex-PM, who is carrying out a media blitz to promote his memoirs, added: "Alex Salmond was saying that Her Majesty would be the proud monarch of an independent Scotland.

"There was a frustration in my team and that's why the conversations between one set of aides and another set of aides took place. But that's it," he declared.

When pressed further he added: "I don't want to say any more because I don't want to make the situation worse than it is."