The Duke and Duchess of Cambridge's lawyers will make a formal criminal complaint to France's criminal prosecutors over an invasion of their privacy, St James's Palace said.
William and Kate have continued their tour of the South Pacific and looked relaxed during their visit.
They appear to have moved on from the furore surrounding the publication of topless pictures of the Duchess, taken while on a private holiday in France last week with William.
A civil action has already been launched by the royals against the French magazine Closer which printed the images and later on Monday the Duke and Duchess will ask the prosecutor to consider charging the photographer who took the intimate pictures.
Once the complaint is made, it is up to the prosecutor to investigate and possibly lay charges over the notorious images published last week.