Lawyers acting for the Duchess of Cambridge have lodged a complaint against French Closer magazine, as an Italian gossip magazine published a 26-page spread of pictures featuring a topless Kate.
Chi, a gossip magazine owned by former Italian prime minister Silvio Berlusconi, also published a feature alongside the pictures asking if Kate's breasts were natural or fake. The magazine ran under the headline 'la regina e nude' - the Queen is nude.
St James's Palace confirmed a criminal complaint over the photographs had been lodged on Monday, with a civil case seeking damages and an injunction preventing further publication due to be launched later in Paris.
Chi published a 26-page spread of topless Kate pictures under the headline 'the Queen is nude'
The palace has said that 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.
French lawyer Aurelien Hamelle is representing the couple. He is the same lawyer who represented John Galliano, disgraced former Dior designer
Duchess of Cambridge talks to a local woman during a visit to the Cultural Village in Honiara
Alfonso Signorini, the editor of Chi, defended the edition saying: "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."
Prince William speaking with Berlusconi in 2009: The former prime minister owns the magazine which published topless pics of Duchess Kate
Chi also published pictures of Princess Diana as she lay dying in the back of a car. Closer is published by the Mondadori media group which also publishes Chi.
The royal's case will be heard in Paris at the Tribunal de Grande Instance de Nanterre and is expected to be held in public.
At the initial court hearing on Monday, the three presiding magistrates said a ruling on whether or not an injunction will be granted would be announced on Tuesday at 11am.
Meanwhile, the editor of the Irish Daily Star has been suspended from his role at the newspaper over the newspaper's publication of the photographs.
Publishers revealed the decision to stand down Michael O'Kane while an internal investigation is carried out into the editorial decision to re-run the images.
The newspaper, co-owned by media baron Richard Desmond's Northern and Shell group and the Irish-based Independent News and Media, has been under threat of closure since publishing the pictures.
In a statement, the company behind the Dublin operation, Independent Star, announced the move.
"Independent Star Limited has suspended editor Michael O'Kane with immediate effect, pending an investigation into the circumstances that led to the Irish Daily Star re-publishing pages from the French magazine Closer, which contained images of the Duke and Duchess of Cambridge," it said.
"Independent Star Limited has no further comment pending conclusion of the joint investigation by the newspaper's shareholders."
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Updated: 18:30 17 September - French court decision
Updated: 20:15 17 September - Suspension of Irish Daily Star editor