Steven Guilbeault is resigning as a member of Parliament, CBC News has learned. 

The Montreal MP and former environment minister is expected to break the news to his colleagues at the Liberal caucus meeting on Wednesday, sources told CBC News and Radio-Canada.

A source with knowledge of his decision said Guilbeault will also speak in the House of Commons Wednesday afternoon to inform his constituents of Laurier-Sainte-Marie about his decision.

Guilbeault, a prominent environmental activist, is quitting the federal Liberals after a series of moves by Prime Minister Mark Carney to roll back key pillars of Canada’s climate and environmental policy.

But in his speech in the Commons, Guilbeault is expected to stop short of blasting the Carney government’s environmental rollbacks and instead strike an optimistic and hopeful tone.

He has kept the Prime Minister’s Office informed of his planned departure, the sources say.

According to a source, Guilbeault was approached about crossing the floor to join another party or even sit as an Independent. He is expected to remain as an MP until the House rises for the summer.

CTV News and the Globe and Mail first reported some of the details of Guilbeault’s departure.

A year into the Carney government’s mandate, it has repealed the consumer carbon tax, eliminated the EV sales mandate, signalled the end of the oil and gas emissions cap and reversed the Liberal promise to end fossil fuel subsidies.

Ottawa is also advancing a number of major projects which are expected to increase planet-warming carbon pollution at home and abroad, including a bitumen pipeline to Canada’s West Coast and numerous LNG export terminals. Those projects are also expected to generate massive provincial royalties, boost the national GDP and help Canada diversify trade from the U.S. 

Many of these reversals included policies that Guilbeault either was involved in championing or spearheaded during his nearly four years as Canada’s environment and climate change minister.

But all of this seemed to come to a head in November when Carney and Alberta Premier Danielle Smith signed a memorandum of understanding for a new energy accord that included a commitment to suspend federal clean electricity regulations which would have had the most impact in Alberta.

“When I entered politics, it was because I had a deep conviction that I could make a difference in fighting climate change and protecting our environment,” Guilbeault wrote in the letter announcing his resignation from Carney’s cabinet soon after that memorandum was signed.

“My commitment to leaving a better world for the future of our children and our planet remains unchanged.”

No longer at the cabinet table, Guilbeault still attempted to create change from within. A source tells CBC News that Guilbeault assisted the government as it crafted its enhanced nature strategy and extended its commitment to international climate finance. 

He also attempted to influence the direction of the negotiations of the Alberta MOU. He vocally urged the government to not compromise on industrial carbon pricing and undermine other climate commitments.

In May, both governments released an implementation agreement that delayed the ramp up of the price on big emitters.

“I’m a good friend of Steven. I’ve worked a lot to bring him into politics and he will always be a good friend,” said Industry Minister Mélanie Joly. “But I also think that what we’ve done with the MOU makes sense.”

“I really want him to stay. I think he is a great guy. I rather have him in caucus saying what he thinks,” said Ontario Liberal MP Marcus Powlowski. 

Some independent estimates state that Canada is not on track to achieve its near term nor longer term net-zero targets by 2050.

Guilbeault entered federal politics in 2019. Before that, he was a prominent environmental activist, founding Equiterre and leading campaigns for Greenpeace.

He captured headlines in 2001 by scaling the CN Tower and unfurling a banner that read “Canada and Bush Climate Killers” — a protest of both Canada and the U.S. failing to ratify the 1997 Kyoto agreement to cut greenhouse gas emissions. Canada ultimately ratified the treaty the following year.

A Greenpeace spokesperson called Guilbeault’s resignation “a red flag” larger than that protest banner.

“[It’s] deeply concerning and underlines what we’ve been saying for months: Mark Carney is prioritizing what is good for oil companies over what is good for regular Canadians,” said Keith Stewart, Greenpeace Canada’s senior energy strategist.