Court documents seen by i reveal that two cases were lodged with the High Court last Friday - one marked Duke of Sussex v MGN Ltd, the publishers of The Mirror, a subsidiary of Reach, and one against News Group Newspapers, the publishers of The Sun, which is owned by Rupert Murdoch.
The details of the case are marked "Business - confidential information". However, the legal firm representing the Duke is Clintons, a London firm which has been involved in representing victims of phone hacking.
Buckingham Palace sources confirmed that claims have been filed on behalf of The Duke of Sussex at the High Court regarding the alleged illegal interception of voicemail messages. The Palace said no details could be made available as the claims are not yet public.
Earlier this week the Prince released an explosive statement about tabloid media coverage, in which he set out his reasons for suing the Mail on Sunday, published by Associated Newspapers, over the way it had reported on his wife, Meghan Markle.
In his statement he said: “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.”
He added: “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 re-purposed as truth across the globe.
"One day’s coverage is no longer tomorrow’s chip-paper.”
He continued: “I have been a silent witness to her private suffering for too long. To stand back and do nothing would be contrary to everything we believe in.
“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.”
The Duke and Duchess have filed a High Court claim against the Mail on Sunday, and its parent company Associated Newspapers, over the alleged misuse of private information, infringement of copyright and breach of the Data Protection Act 2018.
The Mail on Sunday said it would be defending the action vigorously.
According to the website Byline, which reports on Britain's media and first revealed details of the new claim, the current allegations could stretch back to the height of the phone hacking scandal when Britain’s tabloids routinely listened to the phone messages of celebrities and public figures.
It has led to them paying out millions of pounds in compensation.
A spokeswoman for News Group Newspapers (NGN) - which owns The Sun and the now defunct News of The World - said: "We confirm that a claim has been issued by the Duke of Sussex. We have no further comment to make at the current time."
Clintons was unable to comment last night.