Miss Markle, who has written a book about her frosty relationship with her sister called The Diary of Princess Pushy’s Sister Part I, said a part of her could not believe that the Duchess had been “the driving force” behind the biography all along.

“To see her nonchalantly say that she wants to see this added and that added, like items on a lunch menu was astonishing,” she said.

“She’s got an appetite for her own sense of empowerment by doing damage to others.

“My father didn’t want to believe that this smear campaign was all against him, designed to take away his credibility.

“We are victims of a narcissist and narcissists are manipulators who are into domination and control. We are both coming to terms that the denial is over, we have reached acceptance,” she said.

In a series of tweets about the court revelations, Miss Markle suggested that their father should sue the Duchess for “entrapment, elder abuse, defamation” and added that “she doesn’t deserve to have a father”.

She claimed that her sister was “just devoid of a soul,” adding: “Spiders don’t foresee getting caught in their own webs.”

The Duchess’s contact with the authors of Finding Freedom became pertinent when she sued The Mail on Sunday, which had published a letter she wrote in 2018 to her estranged father.

The High Court ruled in February that her privacy had been breached but the newspaper is appealing the decision.

Should the appeal prove successful, the case will go to trial, potentially pitting father against daughter in the witness stand.