Canada's fisheries minister is pushing back against a U.S. company that is refusing to let Canadian researchers test its oil spill dispersant.

"We obviously have a huge concern about a potential corporate interest that appears to not want to have robust, thoughtful, independent scientific analysis of their product," said Dominic LeBlanc.

LeBlanc, speaking in Halifax, was talking about the months-long impasse over his department's attempt to test Corexit 9580, a surface-washing agent used to clean beaches in oil spills.

The product, along with Corexit 9500 — an open-water oil dispersant — were approved for use in Canada last year on a case-by-case basis if authorities determine there is a net environmental benefit.

Impasse over who can test

But Corexit's U.S. manufacturer, Nalco, has refused to provide samples of Corexit 9580 to experts hired by DFO to carry out research of its impacts on capelin, a fish that breeds near the shoreline.

Nalco said it does not allow toxicity testing by non-government agencies.

The third party in this case is fish biologist Craig Purchase and his research group at Memorial University in St. John's. His $75,000 project is funded by DFO.

When DFO made the request on Purchase's behalf, Nalco once again refused to provide a sample.

'Not a sustainable position'

"That is obviously a situation that cannot endure," LeBlanc told CBC News. "It's not a sustainable position."

He said Nalco's refusal prevents his department from carrying out its responsibility to advise Environment and Climate Change Canada, the department that regulates oil spill dispersants.

"Our practice has been to hire experts outside the department, like in the case of Corexit, to do this work," LeBlanc said.

"We'll work with the company and Environment Canada to make sure that that work can be done in a way that is open and transparent to Canadians and offers the best scientific analysis possible."

LeBlanc would not speculate on whether Ottawa would consider delisting Corexit if samples are not forthcoming.

He did suggest co-operating with scientific authorities is one of the best ways to ensure a company's product remains available.

Nalco says it's already provided samples

Roman Blahoski, Nalco's director of global communications, said in a brief email the company provides samples to government agencies for regulatory approval.

However, he said the researches in this case stated they were working with Environment Canada, which had previously been provided with samples.

"We suggested that the researchers connect with their contacts at [Environment Canada] regarding the testing performed by [Environment Canada] labs," he said.