May has not been invited to an exchange of views on the economy hosted by the Globe and Mail newspaper and Google Canada, nor one on foreign policy planned by the Munk Debates.
Prime Minister Stephen Harper, NDP Leader Tom Mulcair and Liberal Leader Justin Trudeau have been asked to take part in these debates.
In both cases, the organizers say they chose to invite leaders whose parties have official status in the House of Commons, which requires at least 12 seats. The Green party, Bloc Quebecois and Forces et Democratie each have two seats.
May has been invited to a number of other events with rival leaders, including one hosted by Maclean's magazine early next month.
Green party spokesman Julian Morelli said in an interview that he privately asked the Globe and Munk organizers to reconsider their decisions, without success.
Morelli said he is "quite stunned" that the organizations would leave May off their invitation lists with no "solid rationale."
"We're not begging to be in these debates with the Globe or Munk, nor should we have to," he said. "This is about Canadians having an opportunity to hear from all the leaders in a forum that's unscripted."
The run up to the general election, expected in October, will see a variety of encounters in different formats — unlike other recent ballots when major leaders debates have been limited to televised exchanges in English and French.
Sean Humphrey, the Globe and Mail's vice-president of marketing, defended the format of the newspaper's planned Calgary event, to be streamed live on globeandmail.com, in partnership with Google Canada, and distributed through YouTube.
"We believe our proposal, and the official parties invited, will lead to focused discussion on the Canadian economy," he said in an email.
Munk Debates chairman Rudyard Griffiths said in May that inviting all six parties with MPs "would unduly limit our ability to hold a substantive debate."
"We really struggled with this," Griffiths said this week in an interview.
"It's somewhat arbitrary to move off the criteria that we've chosen."
Morelli said that's not good enough, stressing that the Green party plans to run a full, national slate of candidates in the election.
In letters to the Globe and Munk, he pointed out that Preston Manning took part in the 1993 TV debate even though the Reform party held just one seat.
May has led the federal debate on climate change, anti-terrorism legislation and Canada's military involvement in Iraq, Morelli said in the interview.
She has been asked to take part in the televised French and English leaders debates to be aired by a consortium of broadcasters on Oct. 7 and 8 respectively.
May has also agreed to participate in the Aug. 6 leaders debate organized by Maclean's that will be broadcast on several television and radio outlets and stream via Facebook and YouTube.
In addition, May received an invitation this week from the venerable Empire Club of Canada to a debate with other party leaders on business and financial issues — the same general focus as the Globe and Google event.
The Canadian Press is jointly owned by the parent companies of the Globe and Mail, the Toronto Star and Montreal's La Presse.
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