Peter spent seven years as a Toronto city councillor before entering and serving in the provincial legislature since 2006. As the Official Opposition's spokesperson on Energy and the Climate Crisis, Peter has advocated for action on climate action, to reduce toxic chemicals, for mercury clean-up at Grassy Narrows, for expansion of renewable energy, and against the end of Ontario’s former cap and trade program. He is an active environmental champion in the legislature, for example through introducing Private Members Bill 224, No Time to Waste (A Plan for Climate Action and Jobs), co-sponsored with MPP Karpoche, and Bill 37, the Liability for Climate-Related Harms Act amongst other environmental legislation. Peter has also served as Executive Director of Greenpeace Canada and climate change advisor to then-federal NDP leader Jack Layton. In 2017, he was awarded a Lifetime Achievement Award from Sustainable Buildings Canada for his lifelong commitment to sustainability.