It was billed as the moment when a wildlife photographer's remarkable patience was rewarded; an image which won him £10,000 and the year's most prestigious award.

But José Luis Rodriguez is now facing allegations that his startling close-up image of an apparently wild Iberian wolf vaulting a farmer's fence is in fact faked.

The judges of the Veolia Environnement Wildlife photographer of the year competition confirmed tonight they were reconvening to determine whether the Spanish photographer had used a tame and captive "model" animal in breach of competition rules.

They have been sent evidence, apparently from rival photographers, that the pictured animal is a wolf called Ossian who lives at a zoological park near Madrid. A wolf expert, quoted by Finnish nature magazine Suomen Luonto, which revealed the allegations, also said the wolf appears to have been trained to jump the gate, because a wild specimen is likely to squeeze between the bars.

Rodriguez could not be reached for comment, but a spokesman for the Natural History Museum, which runs the prize with BBC Wildlife Magazine, said he strongly denied any wrongdoing or breach of the competition rules.

"The museum is aware of an allegation as to the veracity of the photograph, Storybook Wolf, by José Luis Rodriguez, specifically that an animal model was used in breach of the competition rules," she said. "We are investigating this thoroughly with the judging panel and will report back in the new year once our investigations are completed. Mr Rodriguez strongly denies any wrongdoing or breach of the competition rules."

The rules of the competition, which attracted 43,000 entries, state that "images of captive animals must be declared. The judges will take preference to images taken in free and wild conditions".

Rodriguez had told the judges it took him a long time to find the ideal location, let alone a wolf that would jump a gate.

The text accompanying the winning photograph explained: "His chance came when he found a landowner who was happy to have both the wolves and José Luis on his property, and also had the ideal setting: a copse and an ancient, disused cattle corral.

"José Luis started by placing meat in the corral. Once he knew a male wolf was visiting regularly, jumping the gate, he began to introduce the bits of equipment needed to set up a camera trap … When the first transparencies arrived back from the lab, José Luis was overjoyed to find he finally had the picture he had dreamt of."

One wolf expert, Ilpo Kojola of the Finnish game and fisheries research institute, told the magazine that judging by the pictures provided in evidence against the Spaniard, Rodriguez's wolf appeared to be the tame Ossian. "The dark, scar-like sign under the right eye seems to be a unique mark of this individual," he said.

One judge, Rosamund Kidman Cox, told Luonto judges were looking at details such as differences between images presented of Ossian's right ear and that of the wolf in the photo. The picture of Ossian shows the ear apparently damaged and Kidman Cox speculated this may have been the result of a fight. "But until one bit of evidence can be verified I don't think it's possible to accuse the photographer of cheating," she said. "It's not 100%."