Checks are being carried out at Backwell Lake after reports the beauty spot is being used as an unofficial campervan park.
Local residents have reported seeing camper vans parked at the lake at Station Road overnight during the past few weeks.
Some of the vans are understood to have stayed one or two nights, whereas locals are reporting that one has remained parked up for over a week.
Read more: Concern after two swans found dead at beauty spot near Bristol
There have also been reports of the campers emptying their waste water and toilet contents into bushes and drains at the lake - which is home to a number of protected species.
There used to be signs at the lake warning people overnight camping was unauthorised.
It is understood that these were removed during recent work at the lake and are due to be replaced..
The appearance of the campers has sparked concern among local residents who fear it could set a precedent for more to arrive.
And they are concerned about their impact on the wildlife living at the beauty spot, run by Wessex Water.
One resident posted on social media: “Genuine question, is Backwell Lake now a camping site?
Another posted: “The attitude of some is simply shocking.
“£50-100k on a van, and they’re gonna park just where they please.
“Damn the damage, or the rules and laws.
“We can, so we will, is the attitude of way too many.
“They’re the ones spoiling it for others now.
“There are plenty of places that haven’t put fees up, and welcome the business and have the facilities to empty waste etc.”
The lake is well used by local people for recreation and to walk their dogs.
The lake is home to a variety of wildfowl including a flock of swans.
Backwell Lake which feeds into the River Kenn was created in the mid-1970s as an urban drainage system to control flooding.
This is still its primary purpose however the area has evolved into an important site for wildlife and recreation.
Designated as a County Wildlife Site (CWS) and a Local Nature Reserve (LNR) the 20-acre site is surround by marshy grassland, mature trees and dense scrub.
It is home to several protected species including bats, greater crested newts, otters, barn owls, swans, ducks and breeding birds.
Wessex Water said a site visit to the lake had been carried out and that the situation would be monitored.
A Wessex Water spokesperson said: “Overnight camping is not permitted at Backwell Lake and we’ll be monitoring the area out of hours."
Concerns have also been raised about catering vans using the site as a place to trade.
“Catering vans require consent from the council which we require before granting permission at any of our sites," added the spokesman.
"There is currently no such agreement for a van at Backwell.”
The move comes at the same time as North Somerset Council is investigating the possibility of providing a camper van park at Portishead Lake Grounds for people wanting to stay overnight in the district.
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