A further 1500 sheep on the Brecon Beacons will be culled in the latest attempt to halt the foot and mouth crisis.

As slaughtermen moved in on more herds of sheep in the Brecon Beacons on Tuesday, the government revealed that the total cost of the epidemic has now reached £2.8 billion.

The government has also said that there have now been 1906 confirmed cases of the disease in UK.

The move came as a "war zone" was announced in North Yorkshire where 50,000 sheep are to be tested for the disease in a bid to halt a spread into premier pig farms.

Lax farmers who are moving sheep illegally have been accused of causing the latest wave of foot and mouth outbreaks.

Anger among farmers has risen at a government move to scrap the standardised compensation system for those whose livestock are culled as a result of foot and mouth disease.

Police and government officials are also investigating claims some farmers are deliberately infecting their animals in order to take advantage of the payments which in some cases were above current market prices.

The prime minister's spokesman defended the decision saying DEFRA would look very carefully into what were currently only allegations. Downing Street argued when large sums of taxpayers' money was being spent on compensation for farmers who been affected by foot and mouth, it was important to make sure the money was being spent in the right way.

The government ruled on Monday that independent valuers will now decide how much will be paid for animals on each farm on an individual basis.

Animal health minister Elliot Morley said it had now become necessary to revise a system that had been introduced during the height of the crisis.

"The rates were set generously at a time when new cases were being reported at an average of 40 a day to encourage farmers to come forward and speed up the cull, which was vital to bear down on the disease," he said.

Tim Bennett, the deputy president of the NFU, said the union would fight the government's decision.

"There are still 42,000 animals to be culled every week, so it remains crucial that the valuation process is carried out quickly so that the government meets its slaughter targets," he said.