A winning entry from the Wildlife Photograph of the Year competition has been disqualified after it was discovered the photo was of a stuffed animal.

The night raider by Marcio Cabral showed a giant anteater attacking a termite mound covered in bioluminescent click beetle larvae.

The long-exposure image won the 2017 Animals in their Environment category but has since been declared a fake.

The Natural History Museum in London, which runs the annual competition, said it was contacted in March by anonymous sources who questioned the authenticity of the image.

The evidence included high-resolution photographs of a taxidermy anteater that is kept on open display in Emas National Park in Brazil where the photograph was taken.

A photograph of a taxidermy anteater. ( Supplied: Natural History Museum )

"Five scientists, working independently of each other, all concluded there are elements of the animal's posture, morphology, raised tufts of fur and patterns on the neck and head that are too similar for the images to show two different animals," the museum said in a statement.

"The experts would have expected some variation between two individuals of the same species."

Mr Cabral "strongly denies" the anteater is a taxidermy specimen.

The museum said Mr Cabral fully cooperated with the investigation and supplied RAW image files taken before and after the winning shot, none of which included the anteater.

"Mr Cabral did provide an explanation as to why he had no other images of the anteater. He also provided a witness who claims he saw the live anteater."

The museum said it believed the image breached the competition rule that entries "must not deceive the viewer or attempt to misrepresent the reality of nature".

Mr Cabral is no longer considered to be a category winner or finalist.

He is also banned from entering the competition again.

The museum said a new category winner could not be awarded because the judging was meant to be blind.

"As the photographers are now known, it would be impossible for judges to make an objective choice."