Closer magazine in France says it has world exclusive long-lens images of the Royal couple on a private trip to Provence, and has teased the pictures on their website ahead of their planned publication today (14th September).
The mag has also released a pixellated version of the front cover showing three images, with two allegedly of the Prince and Kate together, and another of the Duchess adjusting her bikini top.
The headline reads: "Oh my God! Les photos qui vont faire le tour de monde!" ("Photos that will be broadcast around the world").
According to Sky News, it is currently unknown whether the snaps are legit, and St James' Palace are said to be consulting French lawyers.
A spokesperson for the couple has claimed that Wills and Kate - who are currently on an official tour of Kuala Lumpur - feel "very angered" and believe that "a red line has been crossed" by the publication.
BBC royal correspondent Peter Hunt has stated: "Royal officials say they accept the photos are genuine and the couple are furious. They believe a "red line" has been crossed. The couple cannot believe someone would take such photos and publish them.
"The officials stress the couple couldn't have gone to a more secluded location in France. They were a 'young couple enjoying a holiday'.
He added: "There has been a significant hardening of William and Kate's response to the publication of the topless photos."
A senior palace source has since told The Daily Mail that the incident mirrors the death of William's mother, Princess Diana, in Paris back in 1997, stating: "The Duke and the Duchess were told at breakfast and are obviously saddened and disappointed if they are genuine as they believe they have a right to privacy - particularly on holiday. This incident turns the clock back 15 years."
A second insider concluded: "It is impossible to tell at this stage whether the photographs are genuine or indeed purport to show what the magazine claims, so we are having to wait and see what transpires."
Back in July, an Australian magazine came under fire after publishing snaps of the pair on their honeymoon in the Seychelles.
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