From CP via CTV.ca:

Canada's broadcast networks have denied Green party Leader Elizabeth May a chance to debate the other party leaders on television.

Network officials said that one or more of the other party leaders would refuse to participate in the debates on Oct. 1 and Oct. 2 if May took part.

"The consortium (of television networks) approached the parties to explore the possibility of including the Green party in all or part of the leaders' debates," spokesman Jason MacDonald said in a release.

"However, three parties opposed its inclusion and it became clear that if the Green party were included, there would be no leaders' debates.

"In the interest of Canadians, the consortium has determined that it is better to broadcast the debates with the four major party leaders, rather than not at all."