The Duke and Duchess of Cambridge are to ask France's criminal prosecutors to consider charging the photographer who took topless photographs of the Duchess.
The couple's lawyers will make a formal criminal complaint to the prosecutor over an invasion of their privacy, St James's Palace said.
Once the complaint is made, it is up to the prosecutor to investigate and possibly lay charges over the notorious images published last week in France's Closer magazine.
A palace spokeswoman said: "The complaint concerns the taking of photographs of the Duke and Duchess of Cambridge whilst on holiday and the publication of those photographs in breach of their privacy."
William and Kate's lawyers are also going to the civil courts seeking damages and an injunction preventing further publication.
The case will be heard in Paris at the Tribunal de Grande Instance de Nanterre.
Closer is published by the Mondadori media group which also publishes Italian gossip magazine Chi which has promised a 26-page special edition featuring images of the royal couple on holiday. The palace said no decision has been taken on separate legal proceedings in Italy.
French Closer, which is run by a different company from the British version, caused outrage when it published the images of the couple enjoying private holiday moments at Chateau d'Autet, near Aix-en-Provence.
The decision was roundly condemned but did not put off the Irish Daily Star carrying the images on Saturday, much to its owners' and the palace's fury.
The Duchess's distress was increased when Chi said it would publish more images of the pair on holiday. Alfonso Signorini, the editor of Chi, which is owned by former Italian prime minister Silvio Berlusconi, said: "The fact that these are the future rulers of England makes the article more interesting and topical. This is a deserving topic because it shows in a completely natural way the daily life of a very famous, young and modern couple in love."