The Duke and Duchess of Sussex are to sue the Mail on Sunday over an infringement of copyright and a breach of the Data Protection Act 2018.
The legal proceedings relate to private letters published by the Mail on Sunday and will be funded entirely by the couple.
Legal firm Schillings are representing The Duchess of Sussex.
A spokesperson from the firm said “We have initiated legal proceedings against the Mail on Sunday, and its parent company Associated Newspapers, over the intrusive and unlawful publication of a private letter written by the Duchess of Sussex, which is part of a campaign by this media group to publish false and deliberately derogatory stories about her, as well as her husband.
“Given the refusal of Associated Newspapers to resolve this issue satisfactorily, we have issued proceedings to redress this breach of privacy, infringement of copyright and the aforementioned media agenda”.
If Their Royal Highnesses are successful in their legal bid, the damaged awarded will be donated to an anti-bullying charity.
The Mail on Sunday has not yet commented on the matter.
To coincide with the news that legal proceedings are being launched, Prince Harry released a lengthy statement regarding recent media coverage of his wife.
The Duke said he fears “history is repeating itself” when referring to his mother, Diana, Princess of Wales.
He said: “I’ve seen what happens when someone I love is commoditised to the point that they are no longer treated or seen as a real person.
“I lost my mother and now I watch my wife falling victim to the same powerful forces.”
“Unfortunately, my wife has become one of the latest victims of a British tabloid press that wages campaigns against individuals with no thought to the consequences – a ruthless campaign that has escalated over the past year, throughout her pregnancy and while raising our newborn son.
“There is a human cost to this relentless propaganda, specifically when it is knowingly false and malicious, and though we have continued to put on a brave face – as so many of you can relate to – I cannot begin to describe how painful it has been.
“Because in today’s digital age, press fabrications are repurposed as truth across the globe. One day’s coverage is no longer tomorrow’s chip-paper.”