Animal rights protestors and a number of alpacas are due to descend on Downing Street in a bid to save another alpaca, Geronimo, from execution.
Geronimo, who is six, has twice tested positive for bovine tuberculosis and is set to be euthanised.
The Department of Food, Environment and Rural Affairs (Defra) ordered he be put down, and Geronimo’s owner, Helen Macdonald, recently lost her final appeal at the High Court in London to save her beloved animal.
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Ms Macdonald, who imported Geronimo from New Zealand, believes the bovine tuberculosis tests have been returning false positives but has refused to have him tested a third time.
There has been an outpouring of support from the public to save the condemned alpaca, with more than 90,000 people signing a petition calling on Boris Johnson to stop the killing.
Protesters and a group of alpacas, who have been trained to walk with people and are comfortable around crowds, are expected to gather outside Defra’s headquarters, in Westminster, at 2pm on Monday before marching to the gates of Downing Street.
The demo has been organised by members of the Born Free Foundation, the Alpaca Society, and practising vet and bovine TB policy expert Dr Iain McGil.
The groups believe that Geronimo is free of TB and Defra’s tests are highly inaccurate, and are demanding a different type of test is used to prove his disease status before his death.
Campaigners want the prime minister to force Environment Secretary George Eustice to halt the killing and enforce the latest bovine TB tests for all suspected cases.
Speaking before the protest, Dominic Dyer, from the Born Free Foundation, said: “Defra has known for many years that the TB skin test could be leading to false positive TB results in alpacas.
“However rather than allow Geronimo to be tested for TB using a more accurate Actiphage PCR blood test, Defra secretary George Eustice continues to order his death to avoid greater scrutiny over the many failures in the government’s bovine TB control policy in cattle, alpacas, and badgers.”
Badgers have fallen victim to the fight against the disease, with mass culling introduced to stop the spread of bovine TB since 2013, and demonstrators want to see an end to all cull licences in favour of a vaccination programme.
Writing in the Mail on Sunday, Mr Eustice said: “Farmers understand that infected animals are a risk to the remainder of their herd, so while the loss of individual animals is always a tragedy, the farming communities have worked with our Government vets in this arduous but necessary endeavour.”
Ms Macdonald has threatened to film the last moments of her alpaca’s life if the killing goes ahead and broadcast it on social media.