There is concern that a foam party held at a hotel on the New South Wales mid-north coast has led to the death of fish, platypuses and turtles in a local creek.

Residents discovered the dead fish and other animals along the bank of Coffs Creek at Coffs Harbour after soapy water was discharged through a stormwater drain.

Foam parties are becoming popular at local clubs and hotels, where the dance floor is covered with a metre or more of soap foam.

Ashley Love from the local branch of the National Parks Association says any future parties at the Coffs Harbour Hotel, near the creek, must be better managed.

"The event proposed for Friday night did not go ahead," he said.

"I was personally told by the hotel management there would be no more soaped events, but the council officer was told there would be another one scheduled for New Year's Eve.

"There certainly won't be many council officers patrolling early New Year's Day to see if any soap has gotten into the wastewater system. We're really concerned about that."

Mr Love says the conservationists are not happy with the initial city council investigation.

"We have 10 areas of concern about inadequacies in the investigation that we're at the moment raising with the manager of the Environmental Protection Authority in Coffs Harbour," he said.

The licensee of the hotel that hosted the party said his suppliers guaranteed the product was biodegradable.

He said it has been used in festivals worldwide and he has used it at least half a dozen times in Coffs Harbour without any problems.

The licensee said he is waiting for the result of the investigation before making any further comment.

The Coffs Harbour City Council said it does not know of any problems with so-called foam party runoff polluting Coffs Creek.

The council said it never received any inquiries about such an incident and there is no evidence of platypus in the creek.