Shocked residents believe Siding Lane Nature Reserve in Rainford is attracting people from all over the region who are taking part in the night-time activities.

Officers are now stepping up patrols in the park and have plastered signs throughout the area warning partcipants they face prosecution if caught.

Sgt Paul Holden, of St Helens police, said: "Local residents are right to complain and we will ensure that, along with our partners, we tackle this activity to ensure that the area is amenable to all residents and the wider community.

"I urge those that use the area for illegal sexual activity to stop. Those that continue to undertake in this illegal activity in the area will be dealt with through the criminal justice system."

The practice of so-called 'dogging' involves outdoor exhibitionism in car-parks and wooded areas. The park's dense woodland, secluded pathways make it an ideal location and its 'facilities' have even been advertised on lurdid websites.

Sickened locals and park users say the once peaceful rural idyl has been spoiled by the night-time visitors' antics.

Frank Harford, 59, of Siding Lane, said: "We have lived here for 23 years now, and it has probably been going on for the past three years.

"I've threatened a man who had parked outside my niece's home next door. He wouldn't leave and said he was waiting for someone - as soon as I told him that I was going to phone the police he sped off."

A local angler, who did not want to be named, added: "They all seem to be in their late forties and they do it in the woods and even on the benches.

"They used to do it in their cars but a barrier has been put up to stop them driving down there.

"Now they just do it outside and anywhere - they walk past me while I'm fishing, laughing away like they have the right to do it. It is a disgrace."

The park is run by St Helens Council's ranger service. They regularly host nature walks and recently held a nocturnal tour examining the park's bat population.

However, a council spokeswoman said they did not plan to cancel any events and at the moment there were no local schools visiting the Siding Lane park.

She said: "This is a police campaign and the council is supportive of it as the police are responding to concerns raised by park users."

She added: "Local schools do not use the park as it is too far from the centre of Rainford. Corpus Christi Primary School used to go on visits but they stopped a few years ago due to the distance from their site."