The Duke and Duchess of Cambridge are to make a criminal complaint against the photographer who took topless pictures of the duchess.
The couple's lawyers will make the complaint to French prosecutors on Monday, St James's Palace has said.
The images have appeared in French magazine Closer and the Irish Daily Star. An Italian magazine has said it also plans to print the photographs.
The pair are in the Solomon Islands on their Asian and Pacific tour
A palace spokeswoman said: "We can confirm that a criminal complaint is to be made to the French Prosecution Department."
"It 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."
The couple's legal team will also attend the Tribunal de Grande Instance de Nanterre in Paris on Monday, where damages and an injunction will be sought regarding Closer magazine.