The publication by a French magazine of topless pictures of Prince William's wife Catherine is "grotesque and totally unjustifiable", their office St James's Palace said on Friday.
The couple "have been hugely saddened to learn that a French publication and a photographer have invaded their privacy in such a grotesque and totally unjustifiable manner", the palace said in a statement.
The French version of Closer magazine printed photos on the front cover and inside on five pages of Catherine wearing just the bottoms of a black and white bikini while on holiday with William in Provence in the south of France.
The couple are currently in Malaysia on a tour to mark the diamond jubilee of William's grandmother Queen Elizabeth II.
The pictures are a further headache for the royal family, already reeling from the recent publication of nude photos of William's brother Harry in a Las Vegas hotel.
Another palace source said earlier that the publication "turns the clock back 15 years," the source said, referring to the intense media attention on William's late mother Diana, who died in a car crash while fleeing paparazzi in Paris in 1997.