The catacombs underneath the French capital have long been a popular tourist destination but authorities in Paris are having to battle an unwanted group of visitors wandering through the underground tunnels.

Nude models, photographers and erotic film-makers have been joining the six million skeletons hidden around the city's famous underground chambers, much to the chagrin of those in charge of the catacombs. 

“We receive at least one request [for permission to film or take photos] every week,” a spokesman for the Musée Carnavalet, which manages the catacombs, told French daily Le Parisien on Monday.

“Obviously, we say no. This is a sacred place, which houses the remains of six million Parisians. We only allow serious or scientific documentaries,” the spokesman added.

Denied permission, the underground adventurers take matters into their own hands by disguising themselves as ordinary members of the public to get past the guards.

“These sly people pass themselves off as tourists, hiding all their equipment, like cameras, in bags. Then as soon as they get downstairs, the girls strip off, the crew films without any fuss, and they leave, unseen and unnoticed,” a regular visitor to the catacombs told Le Parisien.

In response to these “constant” naked explorers, the museum has enlisted the help of a crack “catacombs” police squad, to ward off the unwelcome unclothed.

Miru Kim is one of the better-known artists to seek inspiration among the underground tunnels of the French capital.

As part of her 2008 ‘Naked City Spleen’ project, the world-famous American photographer managed to move about naked between winding stone passages, snapping self-portraits along the way.

One particularly striking image features Kim lying nude on her back on what can only be described as a pile of bones.

Shots like that have raised eyebrows for more than one reason, with the management of the Musée Carnavalet telling Le Parisien the photo had been taken “in a chamber that is off limits.”

A spokesman for the Museum Carnavelet played down how frequently those with an ulterior motive for visiting the catacombs, snuck in to take erotic snaps.

“From time to time visitors escape the vigilance of our officers and take unauthorized photos,” the spokesman told The Local. “They are an exception.”

However he added that photos and films are shot in other tunnels underneath Paris which the museum is not responsible for.