Volunteers were set to form a “human shield” to protect an alpaca condemned to death - just hours before officials were due to descend on the owner’s farm to kill the animal.

       Geronimo’s owner Helen Macdonald on Wednesday lost the latest round of her legal battle when the High Court ruled against her.

       But a vet and conservationist has accused government environment officials of using “fraudulent” test data to justify the death sentence, and has issued a last-ditch challenge to them to debate the science with him.

       Ms Macdonald said she would obstruct anyone who went to her farm in Gloucestershire to put down Geronimo, who has been at the centre of a national outcry.

       The alpaca has twice tested positive for bovine tuberculosis, prompting the Department of Food, Environment and Rural Affairs (Defra) to issue a death order, which Ms Macdonald has been fighting for four years.

       Recommended Geronimo the alpaca to be slaughtered after owner loses High Court bid to save him

       Supporters of Geronimo, imported from New Zealand in 2017, say that for the TB tests, Geronimo was “primed” – or micro-vaccinated – twice in quick succession, which caused him to have high levels of antibodies, which in turn caused false positive results.

       And The Independent has seen evidence from the developer of the TB test to the court saying antibodies found in the animal had declined and he had shown no response to the “most specific” antigen.

       Alastair Hayton concluded in his evidence: “Given these observations, and that there is very reasonable doubt from a clinical and epidemiological perspective as to whether the animal is a true M. bovis positive, we would continue to highly recommend caution in interpretation of the results.”

       Vet Iain McGill said: “We’ve got lots of data from alpacas that have been killed after having false positives and they haven’t got TB at all at post-mortem,” he said.

       John Carr-Ellison, a Northumberland farmer, told Farmer’s Weekly how five of his pet llamas had tested positive for TB and were slaughtered – but post-mortem results showed they did not have the disease.

       In some cases, culled badgers that have been analysed after death have been shown to be clear of TB.

       “Defra are trying to kill their way out of trouble – it’s an utter disgrace,” Mr McGill told Talk Radio.

       He said the court failed to force Defra to disclose all its data, adding: “I wonder why officials in the department are making false statements.”

       Helen Macdonald has vowed to defend Geronimo at every step

       (PA)

       He claimed Ms Macdonald was denied permission for a molecular test, which identifies TB bacteria.

       “Helen, while there’s breath in her, will keep the alpaca alive. We will try to save this alpaca - we’ll try to get justice and the right science out there.

       “I challenge Defra’s chief vet to debate with me on this issue.”

       “They’ve killed 140 000 badgers and 300 000 cows in the past 10 years, so why stop when you are on such a successful killing spree. Oh yes, and prevalence of bTB in cows not fallen at all despite all the killing.”

       Defra claims an accuracy for the TB tests of 99 per cent, but that is in animals that have not been primed, whereas the manufacturers have no data for its accuracy in animals that have been primed, Mr McGill said.

       Ms Macdonald, a veterinary nurse, said the battle was about more than just one animal – it was about the reliability of tests Defra uses. “There’s a principle at stake here about valid testing for all animals in the UK, proper science and we’re just not getting it. I’m just disgusted really by the whole attitude," she said.

       A live webcam has been set up in Geronimo’s pen as a surveillance measure.

       A Defra spokesperson said: “We are sympathetic to Ms Macdonald’s situation – just as we are with everyone with animals affected by this terrible disease. It is for this reason that the testing results and options for Geronimo have been very carefully considered by Defra, the Animal and Plant Health Agency and its veterinary experts, as well as passing several stages of thorough legal scrutiny.

       Recommended Badger culls will end after next year, ministers promise – as figures show at least 38,642 were killed last year

       “Bovine tuberculosis is one of the greatest animal health threats we face today and causes devastation and distress for farming families and rural communities across the country while costing the taxpayer around ￡100m every year.”

       Defra declined to say, when asked by The Independent, whether they would use force to get into the pen, and declined to comment on Mr McGill’s challenge of a debate.