The stand-off has become so heated that a government vet has ordered a 48-hour halt to the slaughter in the area while he seeks advice from the Ministry of Agriculture.

The farmers are resisting the culling of about 1,600 sheep unless vets can prove that their stock is infected. They argue that their animals should be blood-tested to see if they carry the virus.

David Parker, the local MAFF vet, has asked Jim Scudamore, the Government’s Chief Veterinary Officer, for guidance on whether testing should be done. He believes the flocks may have been in contact with the virus due to illegal sheep movements in Gloucestershire.

The 25 farmers, who have formed the Forest of Dean Action Group, sent pleas last night to Tony Blair and Nick Brown, the Agriculture Minister, asking for their support.

If the Government insists on culling the animals the farmers are ready to take legal action. They have also organised a telephone chain of supporters to prevent vets entering their premises.

The mood has hardened since farmers heard that vets had proposed a contingency plan to slaughter all animals along the A40 between Gloucester and Ross-on-Wye. It was aimed at culling out the disease if new areas matched the infection levels found in Cumbria and Devon.

Critics of the slaughter policy are unhappy about the ministry’s “scorched earth” strategy for tackling foot-and-mouth.

However, this plan now seems unlikely to be deployed in the Forest of Dean because the area has been free of new cases for ten days.

If Mr Parker is told by the ministry to press ahead with the contiguous cull he will have to ask police to accompany vets to the farms. Farmers who still resist the slaughter will be subject to injunction applications by the ministry.

Sue and Kevin Morgan, of Meend Farm, Ruardean, near Cinderford, are determined to save their 800 sheep and 40 cattle unless there is proof that they are infected.