A Toronto-based environmental group is taking on diamond giant De Beers over its alleged failure to fully report on the mercury levels at its Victor Diamond Mine near Attawapiskat First Nation in Northern Ontario.

The Canadian Parks and Wilderness Society's Wildlands League has filed a legal action against the diamond company after raising concerns last year that mercury contamination near the mine could be higher than the company or the province were letting on.

In a statement, a spokesperson for De Beers Canada said the company has been transparent with its data.

If Ontario isn't going to enforce its own laws, then that's why we felt we had to act. - Anna Baggio of Wildlands League

Mercury and its highly toxic relative, methylmercury, can pose a danger to fish, animals and humans if it builds up in waterways.

Since mining activity can trigger mercury pollution, the Ontario government requires De Beers to self-monitor and report on the mercury and methylmercury levels found in creeks near the open-pit Victor mine — requirements the company says it has followed.

But after studying the diamond mine and its reporting system, Wildlands League has maintained that De Beers didn't report on the mercury levels from all its water monitoring stations.

Though the group says it has received some additional information from the diamond company since raising the matter a year ago, Wildlands League says it is still missing the full picture.

The mouth of Granny Creek, near Attawapiskat: an environmental group is concerned about the effects of mercury on ecosystems there. (Wildlands League)

"The self-monitoring experiment isn't working as it should," says Anna Baggio of the Wildlands League. And the government, she says, is "failing to provide proper oversight."

She adds: "If Ontario isn't going to enforce its own laws, then that's why we felt we had to act."

Wildlands League notified the company Monday it has filed a private prosecution alleging that De Beers violated a condition of its agreement with the province when it did not report on the mercury levels at five of nine water monitoring stations near the mine.

In an email, a spokesperson from the Ontario Ministry of the Environment and Climate Change says the ministry will review the details of the legal action.

Rough diamonds from the Victor Mine near Attawapiskat. (DeBeers)

The ministry also says De Beers is subject to "strict and detailed terms and conditions" surrounding the reporting and monitoring at the mine, and that the ministry worked with the company "to implement a compliance program."

The Victor Mine is currently the only diamond mine operating in Ontario, though De Beers has been exploring other projects in the area.

With the promise of potentially huge mineral deposits in the region known as the Ring of Fire, the region is expected to open up to far more mining operations down the road.

Previous prosecutions

Baggio says Canadians should be concerned about the way governments oversee these projects.

When it comes to monitoring for toxic pollution like mercury, she says, "governments do not have a handle on this."

Ecojustice, the Canadian environmental law group representing Wildlands League, has filed private prosecutions relating to environmental pollution in the past.

In 2009, the group represented an Alberta citizen in a legal action against oil company Syncrude after numerous ducks died from landing in a Fort McMurray tailings pond.

In this case, De Beers has been ordered to appear Jan. 12 at the Ontario Court of Justice, Old City Hall, in Toronto.