King Charles and William, Prince of Wales are said to have erupted into a furious rant when Donald Trump mocked Catherine, Princess of Wales, after she was photographed topless.
The former US president, 76, tweeted about the royal being snapped semi-nude in Provence, France, in 2012: "Kate Middleton is great - but she shouldn't be sunbathing in the nude - only herself to blame... who wouldn't take Kate's picture and make lots of money if she does the nude sunbathing thing. Come on Kate!"
Christopher Andersen's upcoming biography, 'The King: The Life of Charles III' is said by the Daily Mail to say Donald's remarks resulted in "torrents of profanity" from Charles and William, as well as Prince Harry.
The writer added: "Trump's criticism of Kate resulted in what one Clarence House butler referred to as 'torrents of profanity' from both Prince Charles and his sons."
St James' Palace released a statement after a French magazine published the topless pictures of Catherine, calling it a "grotesque" invasion of privacy, and saying: "Their Royal Highnesses had every expectation of privacy in the remote house.
"It is unthinkable that anyone should take such photographs, let alone publish them."
Christopher's book reportedly adds Charles was left "disappointed" when Trump referred to him as the "Prince of Whales" and objected to the former 'Apprentice' judge's boast he could have "nailed" Princess Diana if he had wanted.
The book also says the royal family tried to "discourage" a planned visit by Trump to the UK in 2017, with Charles, William and Harry all said to have set phone lines "burning" to stop it.
It says: "Charles, William and Harry burned up the phone lines between Clarence House and Kensington Palace with all three Princes agreeing to work behind the scenes to discourage Donald's visit.
"Throughout 2017 and into 2018, Britons seemed nearly as fascinated with the tweet-storming Trump as their American cousins. The royal family was no exception. At every opportunity, including Prince Harry's wedding reception, Charles took his wealthy and influential American friends aside and gently prodded them for information."
The Daily Mail said the Palace did not comment on the book.