A French magazine on Friday published what appeared to be photos of Prince William's wife Kate sunbathing topless at a private house in southern France, prompting a strong condemnation from the royal family.
Officials said the royal family was considering legal action for a "grotesque and totally unjustifiable" invasion of privacy in the same country where William's mother Princess Diana died while fleeing paparazzi.
The couple was "saddened" by the use of the photos, which appear genuine, royal officials said.
The revealing pictures of Kate in Closer, a popular gossip magazine, were blurry and shot from a distance. The publication claimed they were taken on a guesthouse terrace in France where the couple vacationed earlier this month.
The first major press incident involving William and Kate brought back memories of Diana being hounded by paparazzi in France in the hours and days before her fatal car crash there in 1997.
Royal officials, who demanded anonymity in line with palace policy, condemned the decision to publish the images.
"Their Royal Highnesses had every expectation of privacy in the remote house. It is unthinkable that anyone should take such photographs, let alone publish them," a St. James's Palace official in London said. "The incident is reminiscent of the worst excesses of the press and paparazzi during the life of Diana, Princess of Wales, and all the more upsetting to the Duke and Duchess for being so."
The palace official said representatives of the couple were consulting with lawyers.
"We feel a line has been crossed with their publication," the official added.
William and Kate, now formally known as the Duke and Duchess of Cambridge, were touring the Far East and South Pacific to mark Queen Elizabeth II's Diamond Jubilee when the photos were published.
No major British publication carried the photos, including Rupert Murdoch's top-selling U.K. tabloid The Sun, which last month ran photos of a naked Prince Harry cavorting in a Las Vegas hotel room.
Media experts in Britain said concerns that Kate's privacy had been invaded would likely mean the images wouldn't be published by the country's newspapers.
They won't get published in this country, and if I was still an editor I would not be publishing them," former News of the World executive editor Neil Wallis told BBC radio. "There's absolutely no chance whatsoever that they will be published in this country."
Wallis, who was arrested last year over the phone hacking scandal at Murdoch's infamous -- and now defunct -- tabloid, said publishing the images would breach British Press Complaints Commission rules on privacy.
The commission -- frequently criticized as a toothless guardian of press standards -- has told British newspapers it is unacceptable to photograph individuals in private places without their consent.
Wallis said there was no justification to run with the images of the duchess, whereas the publication of photographs of Prince Harry naked in a Las Vegas hotel suite was legitimate as it raised questions both about the security arrangements for the third in line to the British throne and also about his judgment.
The British press has been more cautious than usual in the last year because of the phone hacking scandal, which has uncovered widespread intrusion into the private lives of numerous celebrities, politicians and even crime victims.
A spokeswoman for Prime Minister David Cameron, speaking Friday on condition of anonymity in line with policy, said the royal couple was "entitled to their privacy."
She said Cameron -- who had not seen the photographs -- was not appealing directly to editors to refrain from printing the images, but reminded the media that a U.K. inquiry is now scrutinizing how newspapers are regulated.
"Clearly editors are there to make their own decisions, but you know that there is a process ongoing in this country which is looking at the media," she said.
A French lawyer who is an expert in media law said the couple would have clear grounds for an invasion of privacy case. Last week, French first lady Valerie Trierweiler won a judgment of euro2,000 ($2,580) after the publication of photos of her in a bikini.
"French magistrates take into account the victim's behavior, when the person is flaunting themselves on camera. Kate Middleton will get damages because she's not behaving in this way," said the lawyer, Anne Pigeon-Bormans.
It is common for women in Europe to sunbathe topless, both in private gardens and on public beaches.
Pigeon-Bormans said Diana's relationship with the press was more complicated.
"Diana and Kate are two very different people. Diana had an unhealthy relationship with the press, there was an ambiguity: she would flee them, then court them," she said. "I don't feel that with Kate Middleton, she is more balanced."