Mercury contamination from the De Beers diamond mine in northern Ontario may be much higher than the company — or the provincial government — are reporting, according to a new study by the Canadian Parks and Wilderness Society's Wildlands League. 

De Beers denies the allegations, saying in a statement that its environmental data is often misrepresented by other parties.

The Wildlands League study, released Monday and titled Nothing to See Here..., is the result of an 18-month investigation done by the environmental group. It calls for independent environmental monitoring of De Beers Victor mine.

The key concern is that the open pit mine, located in a fragile ecosystem in the James Bay Lowlands, is contributing to the creation of methylmercury, a neurotoxin that accumulates in fish and other food sources of the people who live in the area.

​"De Beers has failed to report on five out of nine surface water monitoring stations, a mandatory requirement of its permit, for the last seven years," said Trevor Hesselink, director of Policy and Research for CPAWS Wildlands League and lead author of the special report. 

"These failures to report important downstream results to the Ministry [of Environment] as required, have shocked us," the environmental group said.

The Wildlands League report draws four conclusions:

  1. Gaps in reporting by De Beers are extensive and persistent 
  2. There are barriers to public access to information about the mine's environmental record
  3. Risk assessment of mercury remains shrouded in secrecy 
  4. The Ministry of Environment and Climate Change struggles to properly oversee this monitoring program 

A spokesperson De Beers said it collects data from 200 ground wells and 15 surface wells and submits "relevant reports" to the government.

"Some sample sites that were relevant in the past may no longer be the most relevant or material now as the mine moved from construction to operations," Tom Ormsby said in an email to CBC News.

Ontario's Mines Minister said he's satisfied that the independent consultant hired by De Beers meets the requirements of the company's mining permit.

"I certainly know that the Ministry of Environment and Climate Change required De Beers to undertake what I think is accurately described as the most comprehensive monitoring plan ever for an Ontario mine," Michael Gravelle said.

The ministry said it recently raised some of the Wildlands League's concerns with De Beers and change has already occurred.

"There are improvements that could be made in terms of how they're presenting the data, how they're organizing it and how they're clarifying it," ministry spokesperson Kate Jordan said. "The company has agreed and committed to doing that."

Hesselink agreed that De Beers recently provided further information to fill some of the gaps in reporting, but he said the new data also revealed concerning discrepancies with past reporting.

"It actually has had the net effect of decreasing our confidence in the [self-monitoring] program in a lot of ways," he said.