Farmers have urged police to crack down on motorcyclists who frighten sheep and chase horses.

There have been reports of motorcyclists deliberately trying to hit lambing ewes and causing a horse to bolt so fast its young rider almost fell off.

The number of incidents of youths using farmland around Brighton as a race track has escalated during recent weeks.

Farmer Martin Carr, 30, pursued a gang of motorcyclists on his quad bike from Pickers Hill Farm, off Saltdean Drive, Saltdean, where they were driving at his sheep, to the edge of Upper Bevendean Farm between Woodingdean and Bevendean.

He said: "They were driving at the sheep and lambing ewes and trying to kill them. It's disgusting. I had to spend hours reuniting the mothers with their lambs. They are terrorising the neighbourhood and we want the police to take some action."

Stuart West, 42, a tenant farmer at Upper Bevendean Farm, said motorbikes went through his corn field and chased his cattle.

He said: "They wreck my crop. Last Sunday, they burnt a stolen bike on the farm. The problem seems to be escalating. The police always seem to have better things to do than chase bikes.

"The police did ask us a few years ago if there was a place on the farm for the kids to race around but there isn't anywhere - that's why they charge around on top of the Downs."

Last month, a 13-year-old girl was almost thrown from her horse when it bolted near Brown Loaf Stables, based at Upper Bevendean Farm. The horse was frightened by racing motorcyclists.

Lesley Morrill, 52, who runs the stables and is chairwoman of The Ouse Valley and District Riding Club, said the child was no longer attending the stables because she was too scared.

She said: "She was screaming. It was by the grace of God she was not thrown off.

"We are in a Catch 22. By the time you inform the police, these motorbikes are gone. Unless there is a proper police presence on motorbikes there is nothing that can be done."

Sussex Police said the growing problem was due to the lack of a purpose-built off-road area for motorcyclists.

It said regular operations involving police officers on their own off-road motorbikes to tackle nuisance bikers would continue.

A spokeswoman said: "Complaints about noisy illegal motorcycles and quad bikes in parks and countryside sites are taken extremely seriously by police.

"As well as motorcyclists scaring farm animals, they have scared away birds, knocked down fences, damaged newly-seeded meadows and nearly run down dogs and their owners as well as injuring themselves.

"If anyone sees illegal motorcycles or quad bikes being ridden on private property or on council land, they are asked to take details such as registration numbers of trailers used to move the bikes and pass them on to the police so the owners can be dealt with."