The winning entry, by the Spanish photographer Jose Luis Rodriguez, beat thousands of entries to scoop the £10,000 prize in October last year, receiving praise for its "fairytale" quality.

But an investigation was launched after suspicions were raised that the picture might breach competition rules.

The judging panel were sent photographic evidence which suggested that the supposedly wild wolf in the picture is in fact a tame wolf called Ossian who lives at Canada Real, a zoological park near Madrid.

Rule 10 of the competition says that photographs of animal models may not be entered for the award and that images will be disqualified if they are entered in breach.

A statement from competition organisers said Mr Rodriguez strongly denies that the wolf is a model.

Owned by the Natural History Museum and BBC Wildlife Magazine, the long-running contest is billed as an international showcase for the best nature photography.

Louise Emerson, from the Wildlife Photographer of the Year competition office, said: "It saddens us to confirm that after a careful and thorough investigation into the image, the storybook wolf, the co-owners of the Wildlife Photographer of the Year competition, the Natural History Museum and BBC Wildlife Magazine have disqualified the winning entry of the photographer Jose Luis Rodriguez.

"The judging panel was reconvened and concluded that it was likely that the wolf featured in the image was an animal model that can be hired for photographic purposes and, as a result, that the image had been entered in breach of Rule 10 of the Competition."

The £10,000 prize money was never awarded to Mr Rodriguez, but he did receive a £500 category winner's cheque, which organisers said they had agreed he could retain in lieu of royalty payments.

They said first place would not be re-awarded as judging is always done "blind" so that an objective choice can be made about the winner.

Miss Emerson added: "Any transgression of the competition rules is taken very seriously and if entries are suspected of breaching the rules they are disqualified. Jose Luis Rodriguez's image will be removed from the exhibition and tour.

"Mr Rodriguez strongly denies that the wolf in the image is a model wolf."