PIG farmers fear their livestock could suffer under continuing movement restrictions imposed to try to control the spread of foot-and-mouth.

Restrictions introduced in the early days of the outbreak have prevented farmers in affected areas from moving their animals, unless they can get a special licence from Maff.

But production methods in the pig industry mean many farmers are facing over-crowding problems, as their livestock continues to multiply but with no way of selling older animals.

John Rider, who farms near Guisborough, east Cleveland, said: "The speed that the modern pig grows and the system farmers have put in place means people have got a production line.

"There are pigs being born every week and they have got to send pigs off to the bacon factory every week.

"But when they can't send them off, there are others coming down the line they don't have space for - and it does give a very serious animal welfare problem."

Mr Rider, National Farmers' Union county chairman for North Riding and County Durham and a board member of the National Pig Association, said that if pigs were kept in cramped conditions they could start to attack each other.

He said: "The major problem is the speed the pig grows, and there are a lot of pigs stuck in County Durham."

Paul Westgarth, a pig farmer near Richmond, North Yorkshire, said the Government's disposal scheme aimed to alleviate the problem by allowing pigs to be moved for slaughter, although there had been delays.

He said: "Pigs are a daily production cycle and it is a different scenario to cattle and sheep, although they also have problems.

"If there is a welfare problem, you are allowed to send them for slaughter now, but this has been slow in getting started."

A Maff spokesman said it was aware of the potential problems, but it had produced guidelines for farmers to ease overcrowding, including using all available buildings or restricting feeds to reduce growth.

He said if all other options had been exhausted, humane destruction may be necessary