Kate and Wills are to make a criminal complaint against the photographer who took topless pictures of the Duchess of Cambridge, St James's Palace confirmed on Sunday night. Lawyers for the pair will make the complaint to the French prosecutor on Monday.
50 pictures of Kate naked are due to be published by Chi on Monday
The couple want the photographer or photographers responsible to be charged with a criminal offence for invading their privacy.
A palace spokeswoman said: "We can confirm that a criminal complaint is to be made to the French Prosecution Department tomorrow.
"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."
Once the complaint is made, it is up to the prosecutors to decide whether to investigate and pursue it.
The news comes as royal lawyers prepare to attend the Tribunal de Grande Instance de Nanterre in Paris on Monday where damages and an injunction will be sought against France's Closer magazine, which was first to publish the notorious images.
The legal action aims to prevent further publication.
Chi Magazine is to print 50 pictures of the Duchess naked
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 but the palace said no decision has been taken on separate legal proceedings in Italy.
The case will begin in the afternoon and is expected to be held in public.
A palace spokesman said earlier today: "The court hearing is in France tomorrow when the official proceedings will start at a court in Paris as the papers have been served.
"It is the first airing and we will be seeking an injunction from them using the pictures and it will lead to a longer court case where damages will be sought."
French Closer, which is run by a different company from the British version, caused outrage earlier this week 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.
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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."
On Sunday, French Closer continued to defend publication of the pictures.
A statement on the magazine's website, said: "The photos we selected are by no means degrading.
"They show a young couple on vacation, beautiful, love, modern in their normal life."
The Irish Daily Star's decision to publish the photographs caused consternation among its joint owners, Northern and Shell and Independent News and Media (INM).
Northern and Shell chairman Richard Desmond said: "I am very angry at the decision to publish these photographs and am taking immediate steps to close down the joint venture.
"The decision to publish these pictures has no justification whatever and Northern and Shell condemns it in the strongest possible terms."
Desmond: 'Northern and Shell condemns it in the strongest possible terms'
An Independent News and Media spokesman added: "The decision by the Irish Daily Star to republish pictures of the Duke and Duchess of Cambridge from the French magazine Closer was regrettable and in poor taste.
"Independent News and Media had no prior knowledge of the decision to publish."
But a boardroom row was on the cards as INM warned it would not be happy to see the tabloid shut down.
A company statement said: "Independent News and Media believes that a call to close the Irish Daily Star, which employs over 120 staff (directly and indirectly), is disproportionate to a poor editorial decision that occurred without reference to either shareholder.
"INM believes that the circumstances that led to the regrettable decision by the Irish Daily Star to re-publish pages from the French magazine 'Closer' warrant immediate investigation and steps are already under way in this regard."
The newspaper was operating as normal today with the newsroom preparing the first edition of the week and reporters and photographers on the beat.
The newspaper's editor, Michael O'Kane, appeared on television yesterday to defend publication but was unavailable for comment today.
Former prime minister Sir John Major backed the decision to take legal action over the pictures and likened the photographer's actions to those of a "Peeping Tom".
"I think it's absolutely right, so that people in the future know where the boundaries should be," he told BBC1's Andrew Marr Show.
"The boundaries have plainly been crossed. I don't think we need minced words about these photographs - the way they have been obtained is tasteless.
"It's the action of a Peeping Tom. In our country we prosecute Peeping Toms.
"That is what they have done, they have been peeping on long lenses from a long way away. they are very distasteful."
He said he "thoroughly applauds" the British press for refusing to use the photographs.
Away from the growing media storm, Kate and Wills put on a brave face on the latest leg of their tour of Southeast Asia, receiving a rapturous welcome from the people of the Solomon Islands on Sunday, who came out in their tens of thousands to cheer their future King and Queen.
Riding in a symbolic war canoe along palm-tree lined roads and with a garland of flowers around their necks the Duke and Duchess appeared a world away from the furore that surrounds the publication of the Duchess's topless photos.
From an open-topped Toyota van decorated to look like a fearsome war vessel they waved and smiled back at the crowds who stood five deep in places.
The Duke and Duchess with His Excellency the Governor General of the Solomon Islands
Kate steps out in traditional Island clothing
The screaming well-wishers lined the royal couple's five-mile route from the airport into Honiara - capital of the South Pacific nation - and a police car with lights flashing and its siren blazing led the way to clear the crowds.
Barbara Daufanamae, 21, a student and friend Frances Vahimana, 22, both from Honiara, had waited for hours in sweltering temperatures to see the royals who are touring the region in celebration of the Queen's Diamond Jubilee, and when they passed were left shaking with excitement.
Daufanamae summed up the mood when she said: "We are just so excited to see them come here. I think almost everyone in Honiara is here.
"This is just so unexpected, it's such a privilege for the country, out of all the countries of the Pacific to have them come here is a privilege.
"Nothing really happens in town so when some body comes everybody comes out and everybody goes crazy."