Robbie Williams believes in aliens and wants to prove their existence in a new documentary

Cape Town - He’s a firm believer in the existence of aliens – and Robbie Williams isn’t ashamed to admit it.

So much so, the British pop singer is set to appear in a documentary to share his experiences with unidentified flying objects (UFOs) and extraterrestrial beings.

The X Factor judge was invited to work on the doccie, called Hunt for the Skinwalker, by his friend George Knapp, The Metro reports.

“Robbie has had a number of encounters that can’t be explained by conventional science and he’s always been very open about them,” a source told Daily Star. “When his friend George asked him to be part of his film he agreed instantly. He’s not embarrassed by his belief.”

Hunt for the Skinwalker will explore the strange sightings found on the Skinwalker Ranch in Utah, America, including mutilated cattle and UFOs.

Among the sightings are bizarre creatures nicknamed “skinwalkers” by the Native American Ute Tribe. It’s believed they’re a type of shape-shifter with the ability to disguise themselves in any form, The Metro reports.

Robbie (44) previously claimed he was once so close to a UFO he could’ve “hit it with a tennis ball”, according to EWN.

“I’ve seen one right above me and if I got a tennis ball out I could’ve hit it with a tennis ball,” he said, adding he definitely wasn’t drunk at the time of the experience. “No substance was involved. No, no substance was involved at all.”

If the documentary’s team are going to push through with their search for otherworldly creatures, they might want to take caution.

“You need to protect yourself. You’re messing with something that’s not good,” said Jeremy Corbell, tribal police officer at the Ute Indian Reservation. “You’re actively hunting it. It’ll hunt you back.”

SOURCES: EWN, THE METRO, DAILY STAR