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.