More than a dozen leading vets have called on the Government to halt the culling of Geronimo the alpaca after questioning his tuberculosis diagnosis, and instead urged the animal to be studied for science.

The 13 vets – who include a former senior official at the Department for Environment, Food and Rural Affairs (Defra) – said they had “grave reservations” about the two positive tests the animal returned in 2017 and they “may well represent a false positive”.

Geronimo’s owner Helen Macdonald has long argued the Enferplex test was fundamentally flawed and says he tested positive because he had repeatedly been primed with tuberculin – a purified protein derivative of bovine TB bacteria.

Defra has ordered the eight-year-old alpaca to be euthanised and a destruction warrant is valid until September 4.

Ms Macdonald, a veterinary nurse, wants the Government to allow Geronimo to be tested for a third time or let him live to aid research into the disease.

Among the signatories to the letter are Professor Ranald Munroe, former head of pathology for Defra’s Veterinary Laboratories Agency and Dr Iain McGill, veterinary scientific adviser to Ms Macdonald.

In the letter, they write: “It is our professional opinion that the diagnosis in Geronimo’s case is unsafe, and may well represent a false positive, due to the fact that Geronimo had been repeatedly ‘antibody boosted’ or primed – five times in his lifetime with four injections of bovine tuberculin and one of avian tuberculin in the run up to the final Enferplex blood test which confirmed the ‘positive’ diagnosis of ‘suspicion of disease’.”

They said Environment Secretary George Eustice had the power to overturn Geronimo’s destruction warrant and order he be observed for scientific research.

“We could learn a great deal from Geronimo were he to be compassionately studied, but very little from his death,” they said.

“We believe Geronimo’s case shines a light on the shortcomings of the current bTB testing policy, and gives an opportunity for a comprehensive review of the bovine TB testing and control policy, based on science and for the health and wellbeing of farmers, cattle, alpacas, badgers, the environment and the public.

“Given the mental anguish that Helen MacDonald has had to endure these past four years, and the publicity surrounding the case, we would urge Secretary of State for Defra, George Eustice and his team to discuss matters with us and Ms MacDonald to find a way out of this impasse.”

Ms Macdonald, who farms alpacas at her home in Wickwar, South Gloucestershire, has received support from around the world – with more than 130,000 people signing a petition against Geronimo’s destruction.

“The letter is quite significant, and I hope the Government take notice,” Ms Macdonald said.

“There are a number of veterinary professionals saying there is no evidence.

“It does show that I have had a valid point for four years and Defra have not listened. We want them to come to the table and resolve it and stop pointing me through absolute torture.

“I feel quite grateful they have come out and said this. It isn’t about being proven right – I want to be understood.”

Last week, a High Court judge refused her lawyer’s application for a temporary injunction to stop the destruction order and reopen the case.

Ms Macdonald said that when Defra officials do attend her farm to euthanise Geronimo, she will not break the law.

Supporters have also been camping out at her farm in case officials Defra arrive to destroy Geronimo.

On Monday, they received a supermarket delivery of tea bags, coffee, sugar and vegan food, which had been organised and paid for by one well-wisher.

As well as alpacas, badgers have been a victim of the fight against bovine TB, with mass culling employed to stop the spread since 2013, sparking a huge public backlash.

The Government insisted all the evidence on the animal’s condition had been “looked at very carefully”.

A Defra spokesman said: “We are sympathetic to Ms Macdonald’s situation – just as we are with everyone with animals affected by this terrible disease.

“While nobody wants to cull animals, we need to do everything we can tackle this disease to stop it spreading and to protect the livelihoods of those affected.”