Three Liberal seats now vacant ahead of byelections
The man who helped design Canada's climate architecture has decided he can no longer live inside it.
Steven Guilbeault, former environment and climate change minister, is resigning as a member of Parliament.
The move is the culmination of a months-long break with Prime Minister Mark Carney's government over a sweeping reversal of Trudeau-era climate policy.
Guilbeault confirmed to CTV News he would address the Liberal caucus Wednesday morning and the House of Commons Wednesday afternoon, where sources told CBC News he is expected to strike an "optimistic and hopeful tone" rather than directly criticise the government.
Sources told the same outlet he was approached about crossing the floor or sitting as an Independent; he is expected to remain as an MP until the House rises for the summer.
The resignation caps a year in which the Carney government repealed the consumer carbon tax, eliminated the EV sales mandate, signalled the end of the oil and gas emissions cap, and reversed the Liberal promise to end fossil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.
The government also advanced a bitumen pipeline to Canada's West Coast and numerous LNG export terminals.
Many of those policies were ones Guilbeault had spearheaded during his nearly four years as environment minister under former prime minister Justin Trudeau.
The tipping point came during the House's recent recess, when the government unveiled major changes to environmental assessments and softened the industrial carbon price through a new accord with Alberta, two Liberal sources told the Globe and Mail.
The accord also paved the way for a new oil pipeline to the West Coast.
Analysis from the Canadian Climate Institute cited by CTV News found the Alberta MOU and corresponding rollbacks risk Canada's 2050 net-zero targets.
A February 2026 report from the same institute found Canada on track to reach only about half its 2030 emissions reduction target.
Guilbeault had already resigned from cabinet in November, hours after Carney and Alberta Premier Danielle Smith signed the initial energy MOU.
According to CBC News, he stayed in caucus hoping to shape policy from within, assisting with the government's enhanced nature strategy and international climate finance commitments, and pushing internally against compromises on industrial carbon pricing.
Carney told the same outlet in a year-end interview that elements of the MOU were amended consistent with Guilbeault's concerns, though he declined to specify what changed.
The departure has unsettled parts of the Liberal coalition.
More than a dozen Liberal MPs wrote to Carney in April questioning changes to methane and clean electricity regulations in Alberta and the delay of the $130-per-tonne carbon price target beyond 2030, CTV News reported.
The letter also raised concerns about potential public funding for a new pipeline.
Caroline Brouillette, executive director of Climate Action Network Canada, told the Globe and Mail that public-opinion polling shows the government's new climate approach could be a vulnerability in key swing ridings.
Green Party leader Elizabeth May called the resignation "heartbreaking," CTV News reported, while Greenpeace Canada senior energy strategist Keith Stewart told CBC News it was "a red flag" that Carney is prioritising oil companies over ordinary Canadians.
Not all Liberals share that concern.
Caucus chair James Maloney defended Carney Wednesday, telling CTV's Power Play that the prime minister's climate credentials are "unimpeachable" and insisting there is "no dissent" within caucus.
Industry Minister Mélanie Joly, who recruited Guilbeault into politics, said she now supports the Carney approach, according to the Globe and Mail.
Shachi Kurl of the Angus Reid Institute told the paper there is also a chance Carney is gaining political capital with the broader electorate, given Canadians' focus on the economy and affordability amid US tariff pressures.
Guilbeault's exit, alongside the upcoming departures of BC MP Jonathan Wilkinson and Toronto MP Nathaniel Erskine-Smith, could pressure the government's 174-seat majority in future byelections, CBC News reported.
Wilkinson has been appointed Canada's new ambassador to the European Union, while Erskine-Smith committed to vacating his seat after running for Ontario's Liberal leadership.
Two Liberal sources told the Globe and Mail they expect the party to hold Guilbeault's riding but cautioned the climate shift could create longer-term liability, given how many New Democrat voters the Liberals attracted in the last election.
