Prince William reportedly threatened Prince Harry with isolation and intimidation.
Royal biographer and author Tom Bower issued the allegation.
He made the revelations in his new book, Revenge: Meghan, Harry and the War Between the Windsors.
In the book, he wrote, "The Palace warned Harry that there would be no further conversation or contact if there were further leaks to the media."
“That, royal advisers believed, would scare Harry. They were wrong,” he added, before concluding.
It comes soon after rumors of tense talks between Prince Harry and Prince William about 'persistently strained relations with the young royals'.