AS the number of confirmed cases of foot-and-mouth disease last night passed the 320 mark, Agriculture Minister Nick Brown warned the epidemic is likely to persist for "several months" yet.

Mr Brown admitted it would take at least three months to wipe away "residual infectivity before we can get our disease-free status back".

The news came as the North-East suffered its blackest weekend of the crisis and the total number of cases for Great Britain rose to 323.

Another four County Durham farms were confirmed as being affected - at Crook, Tow Law, Witton-le-Wear and Shotleyfields - bringing the total to 23.

And in North Yorkshire, where farmers have been praying that the outbreak at Hawes ten days ago would prove to be an isolated case, had their hopes dashed as it was confirmed a second neighbouring herd was infected.

Chief Vet Jim Scudamore said that the outbreak was already far more severe than that in 1967.

"Just three weeks into this outbreak we are already looking at 278,000 animals affected.

"In the six months the 1967 outbreak lasted, only 400,000 animals were affected, which shows the severity of this," he said.

National Farmers' Union President Ben Gill said: "I think the consequences of this disease will mean that there will be movement restrictions on livestock, certainly on sheep, for the foreseeable future, certainly the rest of this year."

Deputy Agriculture Minister Joyce Quin visited Cumbrian farmers yesterday, ahead of Mr Scudamore's visit today, to win support for the controversial mass cull of healthy animals.

Despite the cull being put on hold until after today's visit, the lobby group Farmers For Action vowed an "all-out war".

Andrew Spence, who farms at Leadgate, near Consett, warned that tempers were rising.

"I've had loads of farmers on the phone saying they've had enough and are prepared to do whatever it takes to keep their healthy herds," he said.

"The feeling out there is turning now - people are dead against the culling of healthy animals.

"I hope whoever came up with this policy has a clear conscience."

But Mr Brown said: "The whole country has got to be on the same side and bearing down on the disease, and it is not helpful to try and frustrate the Government's disease control measures.

"Any war being fought should be against the disease, not against the authorities trying to contain it."

Maff was looking at the possibility of making strategic use of vaccination, a proposal he accepted was opposed by "every single person in the industry".

If vaccination were to be deployed, it would only be used on livestock on pasture around known outbreaks to form a buffer zone of inoculated animals, Mr Brown said.

The Centre For Economics and Business Research has estimated disruption from the crisis will cost the UK economy £9bn.

Former agriculture minister and Tory peer Lord Walker attacked the Government's response to the outbreak after meeting Midlands farmers.

He said it was "an unbelievable story of incompetence and lack of action.

"The minister and the ministry should be ashamed.