A public meeting is being called for in Ramsey to discuss plans to make the estuary an Area of Special Scientific Interest (ASSI).
The Department of Environment, Food and Agriculture (DEFA) has stated that it wants to award ASSI status to the Ramsey estuary to limit development.
Elected Ramsey commissioners oppose the plan, claiming it could stifle economic growth within the town.
They intend to arrange a public meeting to canvass opinion in September.
Commissioner Richard Radcliffe said designating the site as an ASSI would be based on incorrect information.
He said: "This area has been developed and is not a natural area because the whole river's been straightened out since the 1860s.
"What was an estuary is now a single mouth to the river.
"It is far from a natural area it is in fact all man-made."