POLICE have been urged to step up their efforts to tackle a bizarre sex craze sweeping North-East beauty spots.

Countryside workers say that "dogging" - where couples get their kicks out of inviting strangers to watch and sometimes join in with them having sex - is increasing in popularity.

There have been fears that the acts are blighting some areas and could be linked to crimes, including blackmail, violence and drug-taking.

An investigation by The Northern Echo has found scores of locations in the region popular with "doggers", many in beauty spots and country parks.

Within seconds of logging on to the Internet, reporters were able to find 11 locations in County Durham, six in Cleveland and nine in the Sunderland area.

One website posting referring to the Hardwick Hall country park, near Sedgefield, County Durham, says that its secluded car parks are a favourite spot.

It says: "Old Bill cruises through from time to time but not a problem. Wait until dark though, as families use the park in the daytime."

Another lists a car park in the village of Newton-under-Roseberry, close to Great Ayton, near Middlesbrough, as being popular with couples and also describes "a toilet with peepholes".

Gamekeeper Brian Pavey, chairman of crime prevention group Darlington Rural Watch, said his members had complained to police about a number of locations where dogging was taking place.

He said: "This thing is growing in frequency and unless it is stopped by the police it will definitely continue spreading."

Doggers can be breaking the law if their actions are deemed by police to be indecent or cause harassment, alarm or distress to members of the public.

But of greater concern is thought to be the safety of those taking part.

Dr Richard Byrne, a senior lecturer in countryside management at Harper Adams College, Shropshire, who has carried out research into the issue, said: "By the time the police get to a specific place the people involved have moved on.

"There is a risk in terms of them being blackmailed into acting against their will or possibly attacked."

The phrase dogging originated from explanations often given to police from those who are watching on, who say they are "just walking the dog".

Inspector Neil Malkin, of Durham Police, said: "We are aware of these websites and have advertised on them to warn that we are patrolling these areas and will enforce the law if necessary.