A Department for Farming and Rural Affairs (Defra) spokesperson said research from their Veterinary Medicines Directorate (VMD) had found residues in fish tissue, wild bird nests, aquatic insects, and coastal waters, suggesting widespread contamination.
Water Minister Emma Hardy is now considering only allowing vets and other medically-trained professionals to prescribe parasiticides, launching an eight-week consultation with the sector.
“This government is committed restoring nature and cleaning up our rivers,” she said.
“We are making progress on reducing the presence of forever chemicals in our waterways and this call for evidence is another important step.
“These treatments play a vital role in pet health and welfare, but it is right that we look at whether they should only be made available for sale via medical practitioners who can advise the public on their correct usage.”
Animal welfare remains paramount, Defra said, and continued access to effective flea and tick treatments for pet owners is a key priority.
A full ban on the sale of fipronil and imidacloprid, is not being considered.
The British Veterinary Association, the RSPCA, and company Bob Martin have been approached for comment.