French paparazzo Pascal Rostain said that the the Royal couple were stalked out at the chateau while on their holiday by an Englishman living in the south of France.
Rostain also sensationally claimed that the photographer was spying on them on the orders of France's Closer magazine, which was first to publish 13 intimate images of Kate and William last week, the Daily Mail reported.
Rostain, in his 40s, is a close friend of former French First Lady Carla Bruni and one of France's most notorious long lens photographers.
"The irony of this whole thing is that the photographer who took these pictures is an Englishman living in the south of France. These photos were taken on the orders of Closer, who asked him to sit around for several days to take them," he was quoted by France Metro newspaper in Lyon as saying.
"For his efforts he did not earn a lot. He could have sold them for 10,000 euros. But in fact he was just paid his wages for going to take them. He didn't put them on the open market either, where he could have earned a lot more," he added.
Another French photographer outside the Chateau d'Autet where the snaps were taken was a French woman named Valerie Suau, nicknamed 'The Sewer' because of the pronunciation of her surname.
She has admitted taking pictures of Kate in her bikini, but said she does not know who took the topless photos.
The Royal couple this week won a landmark injunction preventing further distribution of the images by Closer, under the threat of a 100,000 euro fine.
They have also handed over all files containing the images to representatives of the couple on the orders of the judge, after they were ruled a 'brutal' invasion of privacy.
The court made no ruling for the magazine to name the photographer, however, and it has the right to protect his or her identity under France's laws on protection of journalistic sources.
Meanwhile, a criminal investigation is under way to find and prosecute the photographer, who could face a year in jail and a 36,000 pounds fine.
Yet the photos are still being touted on the open market worldwide, with magazines in Italy, Denmark and Sweden all publishing them.
Rostain did not specifically say he knew the identity of Kate's photographer, but is known to be very well connected among the French paparazzi community.