He was ousted from the Liberal Party caucus and approached the Green Party of Canada to become a member of parliament under the auspices of the Green Party, in the summer of 2008. He never sat in parliament as a Green Party representative as parliament was dissolved in September 2008 before parliament was recalled after the summer session.
He ran as a Green Party candidate, but was defeated in the 2008 General Election.
Having him as a Green member of parliament may have have some bearing on the decision of the Canadian Broadcasters consortium to include the Green Party leader in the televised national leaders debates. Prior to this the consortium was citing that fact that the Greens had no members in parliament as a reason to exclude the Green Party Leader from the televised debates.