Opponents of the controversial Northern Gateway pipeline are fighting federal approval of the project at a hearing today in the Federal Court of Appeal in Vancouver.

The groups hope to block the project, but say the challenges heard this week in Vancouver are important for another reason: to set the tone for whether their relationship with the next federal government is collaborative or confrontational.

Ecojustice lawyer Karen Campbell said the consolidation of 18 legal challenges into one set of hearings is unprecedented.

Haida Nation council president Peter Lantin says this project's approval jeopardizes years of work to build a relationship between his community and Ottawa.

"In the modern history of the Federal Court of Appeal, they have never actually had a hearing this long," said Campbell. "The longest hearing they have ever had is four days, and this one is going to be six days."

Haida First Nation members head into federal court for the hearing about the controversial pipeline project approved in June 2014. (Meera Bains/CBC)

The challenges were consolidated in an effort to streamline them so that they would be heard at the same time.

Eight First Nations, four environmental groups and one union group will present their challenges to the Federal Court of Appeal to underscore why they say the court should revoke Ottawa's approval of the controversial project.

The concerns range from protecting salmon spawning grounds, to First Nations lands rights, to the risks associated with increasing tanker traffic on the B.C. coast.

"One oil spill would devastate thousands of years of dependence on the sea," Gitxaala Chief Clifford White said Thursday before proceedings began.

Responding parties, including the Attorney General of Canada, Northern Gateway Pipelines, the National Energy Board, plus three intervenors, will also present during this set of hearings.

"Enbridge cannot be trusted to build and operate a pipeline that exposes some of our most precious watersheds and ecosystems to the risk of a catastrophic oil spill," said Nikki Skuce, senior energy campaigner with ForestEthics Advocacy, in an earlier press release.

$7-billion project

If built the $7-billion project that would carry bitumen from Alberta's oilsands to B.C.'s coast. The 1,177-kilometre pipeline would traverse 40 First Nations territories and increase tanker traffic on the West Coast by 220 more trips per year.

Northern Gateway spokesman Ivan Giesbrecht, who meets regularly with First Nations groups, says he recognizes their traditional aboriginal land rights, and supports First Nations sharing in ownership and benefits.

"Our ongoing priority is to continue to build trust, engage in respectful dialogues and build meaningful partnerships with First Nations and Métis communities," Giesbrecht said in a press release.

"Despite this litigation, we remain committed to working collaboratively with the applicant First Nations and would be very pleased to develop mutually beneficial solutions with them."

Giesbrecht said the Joint Review Panel's examination of the Northern Gateway project was among the most exhaustive in Canadian history, spanning 180 days of hearings, 80 expert witnesses and 30,000 pages of review.

The Joint Review Panel is an independent body, mandated by the environment minister and the National Energy Board.