The company behind a controversial mining proposal in British Columbia has filed a lawsuit against one of its critics, alleging an environmental group has made inaccurate and defamatory comments that threaten to mislead the public.

Taseko Mines Ltd. (TSX:TKO) filed a notice of claim in B.C. Supreme Court on Thursday targeting the Western Canada Wilderness Committee and one of its employees over statements the environmental group has made about the company's New Prosperity gold and copper project.

The project has faced fierce opposition from environmentalists and local First Nations communities and was rejected by a federal government environmental review in 2010.

Late last year, Ottawa agreed to hear a second environmental review after Taseko promised changes designed to address environmental concerns -- but those changes have done little to quiet opponents such as the Wilderness Committee.

Taseko's lawsuit focuses specifically on postings to the group's website and Facebook account that claim the New Prosperity proposal will harm Fish Lake and Little Fish Lake.

The notice of claim says the online postings wrongly allege the Taseko mine will deposit toxic material into the lakes, turn them into tailings ponds and pollute the headwaters of a major river system.

The company also says the group has wrongly accused Taseko of failing to address concerns raised by a federal environmental review and attempting to deceive the B.C. and federal governments.

The notice of claim, which contains unproven allegations that haven't been tested in court, asks for damages and an injunction to have the online material removed.

"Taseko welcomes a full, thorough and open process to evaluate the merits of the New Prosperity project," Russell Hallbauer, CEO of Taseko, said in a news release issued Thursday.

"We cannot, however, stand idly by when certain parties such as the Western Canada Wilderness Committee mislead the public."

Joe Foy, national campaign director for the Western Canada Wilderness Committee, dismissed the legal action as a "slap lawsuit" designed to silence criticism.

Foy said his group plans to defend itself against the lawsuit, and he suggested the company's notice of claim doesn't accurately reflect what's currently on the Wilderness Committee's website.

Foy noted the Wilderness Committee made changes in recent weeks after complaints from the company. For example, the web page quoted in the notice of claim no longer refers to Fish Lake as a "tailings pond."

"We called Taseko mines and told them we did not think anything we said was actionable, that we were willing to look at the thing that we had up on our website and make some changes, which we did," Foy said in an interview.

"We feel we behaved reasonable in this, but we do not agree that we're guilty of libel so we'll defend ourselves in court."

Earlier this week, a court overturned an injunction that was preventing exploration work at the proposed site, located 125 kilometres southwest of Williams Lake, B.C.

In December, the Tsilqhot'in First Nation was granted a court injunction to stop Taseko from undertaking exploratory work. The band wanted the court to keep the mining firm out of its territory, preventing it from doing any work until the B.C. Appeal Court rules on the band's case involving aboriginal title in certain claim areas.