Wildlife campaigners are warning pest control companies they will be reported to the police if they remove gull nests from rooftops in the nesting season.
East Sussex Wildlife Rescue and Ambulance Service (WRAS) said it was illegal to interfere with any nesting bird, whatever its conservation status.
Spokesman Trevor Weeks said two complaints were lodged last week after incidents in Eastbourne and Peacehaven.
Last year, the demolition of a petrol station in Peacehaven had to be halted.
Contractors had to wait until birds nesting on the roof had flown before they could continue with the work.
Mr Weeks said pest control companies often said they had a general licence that allowed them to remove gulls' nests.
"This licence does not cover the removal of any nest because the parents, nest and young are an inconvenience," he said.
He said WRAS had received numerous reports of cruelty to gulls by both members of the public and pest control companies.
"We have had reports of people hitting gulls' chicks with pieces of wood, using birds of prey to kill nesting gulls and their chicks and live birds being thrown into large bags," he said.
"We have even been called out to gulls with airgun pellets lodged in their bodies, but still alive and in obvious pain."
The herring gull, the most common gull found nesting on rooftops in Sussex, is on the amber conservation list of the Royal Society for the Protection of Birds.