 He served as the Minister of Sustainable Development, Environment and Parks from 2003 until 2006, in the Liberal government of Premier Jean Charest.Elected MP for Outremont in a by-election in 2007, he was named co-Deputy Leader of the NDP shortly afterwards, and won re-election to his seat three times.On May 26, 2011, he was named the New Democratic Party's Opposition House Leader and also served as the NDP's Quebec lieutenant, a post he held until being named party leader.