Green party Leader Elizabeth May plans to appeal to the CRTC over her exclusion from the leaders debates. ((Sean Kilpatrick/Canadian Press))

Green party Leader Elizabeth May sharply criticized Conservative Leader Stephen Harper and NDP Leader Jack Layton on Tuesday, demanding they publicly admit they threatened to boycott debates next month if she were to be included.

"I think we have to out the leaders who secretly threatened not to participate," May said in an interview with CBC News on Tuesday.

Her comments come a day after a consortium of television networks declined to let May participate in the nationally televised debates, saying three parties threatened to boycott but providing no more details.

The Green party will file a formal complaint with Canada's broadcast regulator, the Canadian Radio-Television and Telecommunications Commission on Tuesday, May said.

The party also started an online petition Tuesday demanding May be included in the debates.

Bloc Québécois Leader Gilles Duceppe didn't threaten a boycott, but did express a preference for only the four major parties at the debate, and Liberal Leader Stéphane Dion has said he supported May's inclusion — but wouldn't attend the debate if Harper wasn't there.

"It looks like it's Mr. Layton and Mr. Harper," May said. "I think the Canadian public deserves an answer from each of them. Would they actually refuse to appear on a stage if I was there?"

In arguing against May's inclusion, the Tories and NDP cited a deal she struck with Dion, in which they agreed not to run candidates against each other in their respective Nova Scotia and Quebec ridings.

The NDP confirmed late Monday that Layton had said he wouldn't attend the debate were May allowed to participate, on the grounds that she has already effectively endorsed Dion for prime minister.

"We have someone else who wants to be in the debate who actually supports the leader of one of those [other] parties," Layton said of May.

"I don't agree with that position. I think what we want to do is take on the same old same old, which is the Conservative and Liberal governments in power year after year."

No comment from Harper

When asked by reporters in Winnipeg on Tuesday whether he told the consortium he would pull out of the debate upon May's inclusion, Harper said: "I gather that the consortium has made a decision, and I have no further comment on that decision."

On Monday, Harper said letting May participate in the debates would in essence allow a "second Liberal candidate" to participate, which he said was unfair.

Harper said May would endorse the Liberal party before the campaign was over.

But May told reporters in Ottawa on Monday afternoon that there's "absolutely no way" that she would turn her back on Green candidates running against Liberals and endorse Dion.

Harper was afraid the Greens would cut into his voter base, May said.

"Progressive Conservatives and former Reformers … are really disappointed and disillusioned that Mr. Harper has taken a party whose roots were in grassroots democracy and populism and turned it on its head into a top-down control machine that wants to run over everyone."

May also criticized the consortium for giving in to Harper and Layton's demands, saying it should have "called their bluff."