The prime minister has said he won't take part in the English election debate organized by a consortium of broadcasters, but he will participate in a French one.
NDP leader Mulcair has made it clear he will not participate in any national debate without Harper.
In letters to the leaders, May says it is unconscionable that political parties would undermine and ultimately derail such an important tradition.
She says it would be absurd that only French viewers will see a national debate that reaches all parts of Canada.
May has also written to Liberal Leader Justin Trudeau seeking confirmation of his plan to be in the English debate still scheduled for Oct. 7 — less than two weeks before the election.
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