The complex dune system at one of Pembrokeshire's most unspoilt beaches is being eroded by quad bikes and scramblers.

Although several farmers have diversified by establishing quad bike trails, the National Trust says people are increasingly targeting the sand dunes which border Freshwater West beach.

Marram grass, the key vegetation which traps wind blown sand and binds the dunes together, is being damaged in the process and their long-term stability is under threat. The beach is jointly owned by the National Trust and the Angle Estate and by-laws are in place to prevent people riding about on it with bikes.

But the remoteness of the beach means these by-laws are difficult to police and the owners rely on the public to supply them with the registration numbers of the culprits. Richard Ellis, head warden for the National Trust in Pembrokeshire, urged bikers to stay away. "Don't come to Freshwater West, that's the bottom line," he said. "You should find somewhere where you can ride your buggies legally with the landowner's permission.'' Prosecution, he admitted, was a weapon of last resort because it was a lengthy and costly process.

A warning, he stressed, was usually enough for most people. "It is much better if the people responsible can be identified by their registration numbers and spoken to, perhaps by the police.

Pictured: Richard Ellis. PICTURE: Debbie James.

"If we catch someone, which is not always easy, we speak to them ourselves. With sensible people a warning is usually enough.''

The people responsible were predominately local, added Mr Ellis. "It is a remote spot and it is difficult to keep an eye on the place, which is why we are grateful to members of the public for being eyes and ears when we are not there.''