David Cameron's revelation that he sought help from the Queen ahead of the Scottish independence vote in 2014 has caused displeasure at Buckingham Palace, a source says.
The former PM told the BBC he had asked whether the Queen could "raise an eyebrow" about the prospect of Scotland voting for independence.The Queen later said people should "think carefully about the future".
Buckingham Palace has made no official comment on Cameron's remarks.
The revelations were made in a two-part BBC documentary in which the former PM reflects on his time in Downing Street.
What was discussed was not "anything that would be in any way improper... but just a raising of the eyebrow even... a quarter of an inch", he said.
The source told the BBC that "it serves no one's interests" for conversations between the PM and the Queen to be made public .
"It makes it very hard for the relationship to thrive," they added.BBC royal correspondent Jonny Dymond said the source's words suggested "something coming pretty close to real anger" at what Mr Cameron said.
Just as the first rule of Fight Club is that you do not talk about Fight Club, the first rule of the relationship between the prime minister and the Queen is that you never, ever talk about the relationship between the PM and the Queen.
It is difficult to imagine anything other than horror in the Palace at David Cameron's revelations. Not just because he has broken the first rule. But because he has made it painfully clear that in 2014 he used the Queen for his own political purposes. And that she and her advisors thought that was OK.
The revelation comes as her suspension of Parliament - a suspension made on the effective instruction of Boris Johnson - comes under unprecedented scrutiny in the Supreme Court.
The two cases are very different; but they both highlight the dark greys of the Queen's constitutional position, the discretion she has or lacks, under extraordinary circumstances, to speak out and act.