OTTAWA -- The federal Greens have filed a complaint with the Canada Revenue Agency in a last-minute bid to use the law to get their leader into an election debate later this month.

The Munk debate takes place one week from Monday and yet again Elizabeth May won't be on the stage with Stephen Harper, Tom Mulcair and Justin Trudeau.

To get her on the panel with the other leaders, the party has filed a complaint with the CRA saying the debate format violated the agency's policies that put limits on the political activities of charities.

The Aurea Foundation, a registered charity with the CRA, is helping fund the Munk debate on foreign policy.

The Greens argue that excluding May from the debate has put the foundation in violation of the Income Tax Act. The law says it's illegal for a charity to directly or indirectly support or oppose a political party and are calling on the CRA to conduct an immediate audit of the charity's activities.

The party says it will withdraw the complaint if May is invited to the debate.

Munk debate organizers, the Aurea Foundation and the CRA could not be reached for comment Sunday.

In the letter sent to the CRA, party executive Emily McMillan writes that May was excluded from the debate because organizers only wanted to have the leaders of parties recognized as such under the Parliament of Canada Act.

With only two seats in the Commons, the Greens don't have party status. But McMillan argues there is nothing in the Parliament of Canada Act to limit the meaning of "political party" that would "justify the exclusion of Ms. May from the debate."

"The effect of not including Ms. May is to diminish the standing of the Green Party of Canada in the mind of the electorate, which amounts to an indirect opposition to the Green party," McMillan wrote.

"The way that the Aurea Foundation is organizing the debate constitutes, we submit, support for the political parties whose leaders are being permitted to participate in the debate."

Similar letters signed by a party lawyer were delivered to the venue, Roy Thomson Hall in Toronto, the broadcaster, CPAC, and Munk debate organizers, the Greens said.

May was not invited to take part in a debate on the economy last Thursday organized by The Globe and Mail. Instead, she tweeted her responses to questions and delivered her own zingers to an online audience.