VANCOUVER -- As opponents of the Trans Mountain pipeline expansion protested across the country Monday, Canada's environment minister said the project needs to move forward.

Protesters gathered outside the offices of Liberal MPs calling for Prime Minister Justin Trudeau's government to pull its support for the controversial pipeline.

The rallies follow Ottawa's announcement last week that it will spend $4.5 billion to buy the pipeline and ensure the expansion project is completed.

"The crazy buyout of this pipeline project has actually united people from the left and the right," said Peter McCartney, a climate campaigner for the Wilderness Committee, who led the rally outside Justice Minister Jody Wilson-Raybould's office in Vancouver.

Jolan Bailey, a campaigner with advocacy group LeadNow, said more than 100 events were held in cities across the country, including Calgary, Regina, Toronto and Halifax.

A rally in Environment Minister Catherine McKenna's riding of Ottawa-Centre drew more than 100 people, Bailey said.

"There are a lot of people that are frustrated with a government that campaigned on making climate action a priority, but now has not only approved a pipeline ... but (Trudeau) is actually using our taxpayer dollars now to pay for the project," he said.

Outside the House of Commons on Monday, McKenna reiterated her government's support for the pipeline expansion and said it's time to move on.

"A decision was made, as I say, by the federal government over a year ago. Also by the former government of British Columbia. We need to provide certainty to investors and we also need to bring people together," she said.

"The environment and the economy go together and this project will go ahead."

In Vancouver, about 100 people attended the protest, holding signs saying "No consent, no pipeline" and "Not justifiable" and chanting "Keep it in the ground."

Sarah Green joined the chanting while holding her one-year-old son.

"I just think it's important to show that people of B.C. don't want this pipeline," she said. "And we especially don't want to be paying for it. I think we made it really clear."

Green's father, Bill Bargemen, said he came to the rally because he's concerned about the impact the pipeline could have on his grandson's future.

"This little guy may well live into the next century and I'm really terrified about what that's going to look like if we don't come to grips with climate change," Bargemen said.

Opponents are attacking the project on a number of fronts and that will continue until the project is shelved, Bargemen said.

"It's going to be done in the courts, it's going to be done in the streets, it's going to be done at the ballot boxes, it's going to be done when people are willing to go to jail and they're doing that," he said. "This is the line in the sand. We have to take this stand now."

Dozens of people have been arrested outside Kinder Morgan's facilities in Burnaby, B.C., in recent months, including Green Party Leader Elizabeth May and New Democrat MP Kennedy Stewart, who both pleaded guilty to breaking a court injunction barring protests near Trans Mountain worksites.

In Parliament on Monday, opposition members attacked the Liberal government over news that two executives for Kinder Morgan will each be given $1.5-million retention bonuses to ensure they stay on as the Trans Mountain pipeline system is sold to the federal government.