CALGARY - Ottawa wants the Commission for Environmental Co-operation to drop its investigation into whether laws are being properly enforced when it comes to oilsands pollution.

The CEC asked the federal government in December to respond to allegations that it has failed to enforce provisions in the Fisheries Act by allowing harmful substances to leak from tailings ponds into water sources downstream of mines in northeastern Alberta.

But the federal government said in January that process should proceed "no further" because a legal case dealing with the same issue was already underway in provincial court. In April, the CEC said it disagreed with Ottawa's stance and would press on with its analysis.

Last week, Environment Canada reiterated its view, but with stronger language, saying the process should be "terminated" because the CEC was acting "contrary to its authority," assistant deputy minister Dan McDougall wrote in a letter posted on the commission's website.

In 2010, two environmental groups and three individuals made their complaint to the CEC, which was created alongside the North American Free Trade Agreement as an avenue for Canada, the United States and Mexico to address environmental issues.

The commission can't compel member governments to do anything, but the complainants hope it will compile a "factual record" that will draw international attention to the issue.

Environment Canada argues the commission can't continue with its probe while a separate proceeding into the same issue is ongoing — in this instance, a case spearheaded by a citizen of Fort McMurray Alta., involving oilsands giant Suncor Energy Inc. (TSX:SU), currently in provincial court.

"Both the Government of Canada and the Province of Alberta are effectively enforcing their environmental laws," McDougall wrote. "Canada and Alberta are prepared to take the exceptional measure of providing additional information further to the goals of the (North American Agreement on Environmental Co-operation) that will provide details on our ongoing enforcement actions."

However, he said the federal and provincial governments won't be in a position to do so until the legal case has worked its way through the courts, which is expected to be in late August.

"We maintain that our intention in providing this information is without prejudice to Canada's position that the Secretariat has acted contrary to its authority by the (North American Agreement on Environmental Co-operation) and that the current submission should be terminated."

However, Environment Canada said it still backs the work of the CEC overall.

"Canada continues to support public participation in the Commission for Environmental Co-operation as it brings citizens and governments together on key environmental issues in North America," department spokesman Danny Kingsberry said in an emailed statement.

Hannah McKinnon, with Environmental Defence, described Ottawa's response "brazen" and says it's another example of the federal government trying to stifle scrutiny of oilsands development.

"Certainly what struck me the most about this letter was just the language and tone that they used. It really does feel like the latest in this pattern they have in attacking anything that is getting in the way of their tarsands expansion plans," she said.

"The CEC is doing exactly what it's supposed to do, which is to take a close look at these environmental concerns."

McKinnon says the federal government in the past has also "attacked" environmental organizations, "gutted" environmental laws and limited the public's involvement in pipeline hearings.

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