Canada's federal court of appeal has overturned approval of the new Northern Gateway pipeline on grounds that builders failed to adequately consult with affected aboriginals, documents released Thursday revealed.

The oil conduit stretching nearly 1,200 kilometers (745 miles) from the Alberta oil sands to the Pacific coast received regulatory and government approval in 2014, with 209 conditions to mitigate environmental impacts.

But nine indigenous tribes with ancestral lands along the route asked for a judicial review of the decision, arguing that the process failed to meet a constitutional duty to engage aboriginal communities.

The federal appeals court agreed.

"Canada offered only a brief, hurried and inadequate opportunity... to exchange and discuss information and to dialogue," the court said in its decision, released by lawyers for the plaintiffs.

"The inadequacies -- more than just a handful and more than mere imperfections -- left entire subjects of central interest to the affected First Nations, sometimes subjects affecting their subsistence and well-being, entirely ignored."

Enbridge first proposed in 1998 construction of the pipeline to move 525,000 barrels of crude per day from Edmonton, Alberta across rugged mountain landscapes to a new marine terminal in Kitimat on British Columbia's northern coast, for shipping to Asia.

Aboriginals and environmental activists, however, feared a spill from tankers at the terminal could damage the pristine coastline that includes salmon-bearing rivers and the habitat of a rare white bear.

"This is a major victory for the First Nations, whose rights and interests were ignored in the assessment of the project's costs and benefits," lawyers for the Gitxaala tribe said in a statement.