The government is on the verge of being sued for �7bn over claims the foot-and-mouth outbreak actually happened months before it was officially recorded.

The Department of Environment, Food and Rural Affairs (Defra) has always maintained that the first recorded case in the last epidemic was 20 February 2001.

But lawyers acting on behalf of 1,500 rural businesses now claim that a farmer in Wales had a confirmed case in October 2000.

London firm Class Law has a statement from a witness which they say confirms this - and this month, a microbiologist employed by the partners will test the cattle carcasses which they are asking to be exhumed.

Substantiated

There are further claims that pigs in the West Country were also contaminated long before February 2001 and buried without an official record being made of them having the disease.

In both cases there is, as yet, no scientific evidence to support these claims.

On Tuesday, Defra reiterated to BBC News Online that the outbreak began in 2001.

A spokeswoman said: "I have checked with our vets and the first recorded case was in February 2001."

But she added: "When we receive the letter [from Class Law], we will look at it."

A spokeswoman for the National Farmers' Union (NFU) said claims that the outbreak actually began earlier had often been "bandied around" and she did not think the latest claims would be substantiated.

But Stephen Alexander, a partner in Class Act, said they had a large dossier of evidence, including statements from witnesses and farmers.

He added: "We are going to send a letter to Defra today [Tuesday] which will include all the evidence we have.

Fighting fund

"Our microbiologist says he will be able to do tests on the carcasses which should still show traces of the disease if it is there.

"More and more evidence is coming out every day."

If Defra "does not respond satisfactorily" a writ will be issued with the High Court suing the UK Government for �7bn in compensation, Mr Alexander added.

The group action could mean ministers are summoned to court to face allegations of negligence over their handling of the epidemic that cost the industry dearly.

A NFU spokesman said the union had taken advice from counsel on the issue of earlier outbreaks and compensation but had been told there would be "a number of very high hurdles" to climb in order for it to be successful.

The union had not been approached by Class Law, he said, but it was up to individual farmers if they wanted to join them.

A fighting fund of �2m has been set up and organisations already backing the case include the Youth Hostel Association and the Aberdeen Angus Steak House chain.

So far, 1,500 rural businesses have pledged their support but up to 25,000 could potentially join the action.