Farmers were last night hit with a further outbreak of a disease thought to have cost the industry £250m since August.

The National Farmers' Union (NFU) said the new case of foot-and-mouth at a farm in Surrey would have severe financial implications.

The Department for Environment, Food and Rural Affairs (Defra) last night confirmed the disease had been found on an eighth farm.

It follows Saturday's announcement that animals had been slaughtered after showing symptoms of the virus.

The farm is within the current protection zone around previously infected farms and minor changes are now being made to the zone.

Defra said cattle at four other farms close to the latest outbreak, near Wraysbury, would also be culled after being exposed to the infection to "such a degree that they are likely to develop disease".

A spokeswoman said a programme of "intense surveillance and blood testing" would continue in a bid to identify any further cases. She urged farmers to remain vigilant and check their animals twice a day.

Anthony Gibson, spokesman for the NFU, said the industry had prepared itself for last night's confirmation that the disease had spread.

He said: "The longer we keep getting these outbreaks, the longer it will take to get the export ban lifted. And that's costing at least £2m a day.

"Since the foot-and-mouth outbreak was confirmed in August, we think the total cost to the farming industry is around £250m. That's in terms of lost exports and lower meat prices.

"I think the vets are going to have to do some intensive surveillance of cattle in that area because we really must knock the virus on the head as quickly as we can."

The latest outbreak of foot-and-mouth comes at a time when England's farming community is already reeling from the UK's first cases of bluetongue disease.

But Mr Gibson said this was "less of a concern" to farmers.

"There are a number of possible new cases of bluetongue under investigation but that's not surprising," he said.

"When animals are off-colour, farmers are likely to report it as a possible case of bluetongue.

"But there's no sign yet that it has spread out from the Suffolk area where it was first identified. At the moment, bluetongue is less of a concern than foot-and-mouth disease."

Bluetongue control and protect zones are now in force in parts of Norfolk, Suffolk, Essex and Cambridgeshire.

Vets have confirmed 11 cases of the virus - ten in the Ipswich area and one near Lowestoft.