Hyer announced in December that he was joining the Greens — doubling the federal party's elected caucus from one member to two.
The new title gives him a say in the party's internal operations, including fundraising efforts.
The MP for the northern Ontario riding of Thunder Bay-Superior North was first elected in 2008 under the NDP banner, and again in 2011.
But Hyer left the New Democrats in April 2012 after breaking ranks with the party over its defence of the long-gun registry, citing his exclusion from the party's shadow cabinet and what he called the "mindless solidarity" of party discipline.
Hyer and May say there will be no lock-step voting in Parliament for the Green party caucus; May says she actually looks forward to the first time she and Hyer vote on opposite sides of an issue.
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