The federal government has approved the controversial Trans Mountain pipeline expansion for a second time, a decision that triggered a protest in Vancouver on Tuesday.

Prime Minister Justin Trudeau announced the government's renewed support for the project, which is expected to triple the amount of fossil fuels funneled into B.C. through the pipeline, just one day after the Liberals introduced a motion declaring climate change a national emergency.

Trudeau argued the goals of protecting the environment and addressing climate change can be reconciled with the expanded sale of Canadian oil.

"In order to bridge the gap between where we are and where we're going, we need money to pay for it," he told reporters. "Canada is blessed with natural resources, and with that comes major responsibility. As the world transitions to a cleaner economy, there will be demand for our existing resources."

Some environmentalists disagreed with that rosy-ways assessment, however.

“How can Canada, as wildfires and floods rage all around us and our citizens are forced to flee their homes, choose to make the climate crisis worse?” Peter McCartney of the Wilderness Committee said in a statement. “Building the Trans Mountain pipeline is a slap in the face to every young person across the country who worries for what a hotter future holds.”

The previous approval was overturned last summer by the Federal Court of Appeal, which found the government had failed to properly consult with Indigenous communities or consider the impact increased oil tanker traffic would have on marine life.

The new one follows a renewed and sincere effort to meet those obligations, Trudeau said.

"We needed to do better," Trudeau said. "We listened to community concerns and we are acting on community ideas."

Some of the priorities highlighted in the government's consultations included the protection of salmon habitats in the Fraser River and the southern resident killer whale population off the coast, according to the prime minister.

The approval was widely expected given that Ottawa spent $4.5 billion purchasing the pipeline last year. Anticipating the government's decision, activists in B.C. organized a protest in downtown Vancouver that drew dozens of people Tuesday evening.

Pipeline opponents gathered near Georgia and Hamilton streets to listen to speakers.

B.C. Premier John Horgan, who campaigned on a promise to fight the pipeline in the last provincial election, acknowledged the federal government's jurisdiction in approving the project.

"Although I regret the federal government's decision, it is within their authority to make that decision," Horgan said. "We know that British Columbians continue to be deeply concerned over a sevenfold increase in tanker traffic in the Salish Sea."

Horgan also promised to approve the permits necessary for the project's construction to move forward – but only if they comply with the environmental conditions set by the National Energy Board.

The premier also said B.C. still intends to bring its reference case to the Supreme Court of Canada, to seek clarity on whether it has a right to impose restrictions on oil shipments in the name of protecting its coast.