VANCOUVER -- A B.C. First Nation has launched a lawsuit in an attempt to stop a struggling, but potentially lucrative, mine in the northwest corner of the province.

The Taku River Tlingit has filed a notice in B.C. Supreme Court, alleging the Tulsequah Chief Mine project must be stopped because it will significantly harm the band's way of life.

The proposed zinc, copper, lead, silver and gold mine is perched in the Taku River watershed, a region rich in wildlife and salmon that straddles the border between northwestern B.C. and southeastern Alaska.

The band's lawsuit says environmental approvals for the mine have expired, the province failed to consult about the project, and the decision-making process is flawed.

The band says in June 2012, six months before the mine's environmental assessment certificate expired, B.C.'s Environmental Assessment Office allowed the certificate to remain valid because owner Chieftain Metals had "substantially" started the project.

But the Taku River Tlingit's notice of claim, which contains unproven allegations, says none of the mine's main components has ever been constructed and the extension was invalid.