A federal New Democrat is calling on the courts to order the party to let him run in its contest to replace Tom Mulcair as leader, court filings show.

In his application to Ontario Superior Court slated to be heard on Tuesday, Brian Graff accuses the party of violating its own rules when it repeatedly disallowed his candidacy.

The party, however, maintains it would be "extraordinary and unprecedented" for the court to decide whether Graff would be suitable entrant and wants the application tossed.

Story continues below advertisement

"Making such a determination is purely partisan political activity," the party argues in court filings. "It would be inconsistent with democratic values and inappropriate for the judiciary to enter the political arena as the arbiter of who is suited to seek the leadership of a federal political party."

Graff, 58, who ran unsuccessfully for a Toronto council seat in 2014, was a Liberal activist for most of his adult life. However, he says he became disillusioned with the Liberals after Justin Trudeau came to office in 2015. He joined the New Democrats in August last year. On his wish list is a "full employment" policy.

"While he is a relatively new member of the NDP with some ideas that challenge party orthodoxy, Mr. Graff meets all candidacy requirements in the NDP's leadership rules," his court application states. "Yet the NDP – specifically, executive director Robert Fox and four party officers serving as an appeal committee – has now twice rejected Mr. Graff's candidacy, citing a series of shifting and irrelevant reasons."

Graff maintains the party relied on "vague and highly subjective" factors in barring him from the race, which he first tried to enter in October. Those factors include whether a candidate's actions, beliefs or attitude could hurt the NDP's reputation.

The party initially rejected Graff late last year without saying why. Graff then asked the courts to get involved, but abandoned the action after the NDP agreed to take another look at the situation, and provided him with Fox's internal emails regarding his candidacy.

Among other things, the emails note Graff's "history of litigious behaviour" and previous criticism of the NDP, the court filings show.

"We can anticipate Brian will protest his rejection which also entails some risk," Fox wrote. "But I'm inclined to think the short-term hit is much less potentially damaging than his continued participation in the race."

Story continues below advertisement

What was not in the emails, the filings state, was any reference to the fact that Graff received a conditional discharge in 1993 for a non-violent offence involving criminal harassment of a woman.

In April, following the promised second look, Fox cited the long-ago charge in again rejecting a Graff candidacy.

"Given the...justified public concern about issues of stalking and intimate partner violence, accepting an applicant who has been found guilty of such a crime would seriously damage our reputation, alienate a significant portion of our membership and undermine confidence in the party," Fox wrote in a letter now part of the court record.

Graff, however, argues the party has treated him badly.

"No reasonable explanation exists for this wholesale shift in the NDP's rationale for rejecting Mr. Graff, apart from a transparent attempt to discredit, embarrass and disqualify him at all costs," his factum states. "The NDP's contrived rationales for excluding him find no support in the record. They are illogical, unjust and unreasonable."

In response, the party argues that Graff may disagree that his "criminal conduct and lack of recognition or remorse for that conduct" could damage the NDP, but says there's nothing unreasonable about concerns that they could.