Council officials are set to install a barrier to the entrance of a Rainford nature reserve to prevent it being used as a dogging hotspot.
There will also be a row of boulders positioned down one side of a road at Siding Lane Nature Reserve.
Police and council chiefs believe the park is one of the most popular haunts for dogging in the region.
The practice involves people parking up in car in order for the occupants to indulge in public sex orgies.
A spokesman for St Helens Council said: “An order has been placed to install a barrier across the car park area which will be locked at night by our security section and reopened again in the morning.
“Parking on the roadway will be restricted by placing large boulders down one side of the road to stop cars parking up, and the ranger service, grounds maintenance, security staff and Merseyside Police will be working together to monitor the situation.”
In March, police warned that the park was being used for dogging.
At the time, Sgt Vicky Holden said: “I would urge those using this area for illegal sexual activity to consider the distress and environmental damage that this causes.”
Anyone with information relating to this activity can call the neighbourhood team on 630943, via 101, or Crimestoppers anonymously on 0800 555 111.