NDP Leader Tom Mulcair campaigned in Edmonton with Alberta Premier Rachel Notley on Friday, hoping to repeat her come-from-behind win on the national stage.

With polls suggesting Mulcair’s party is trailing the Liberals and Conservatives, he tried to fire up voters.

“They said we’d never win in Alberta, but with Notley, you all proved them wrong,” Mulcair told supporters.

He spent much of his time hammering away at Liberal Leader Justin Trudeau, seizing on the resignation of the Liberals’ national campaign co-chair, Dan Gagnier.

The NDP has filed an official complaint with the Commissioner of Canada Elections regarding Gagnier, who stepped down from his post after an email came to light, in which he advised an energy company on how to lobby a potential new government.

Anne McGrath, the national director of the NDP, submitted a letter to the Commissioner of Canada Elections on Friday, calling for an investigation into Gagnier, the Liberal party and the TransCanada Corporation for a possible "contravention of the Elections Act."

In her letter, McGrath suggests Gagnier and TransCanada may have violated various prohibitions under the Elections Act dealing with election contributions, as Gagnier was being paid by TransCanada while working as a volunteer on the Liberal campaign. TransCanada is the company behind the Keystone XL and Energy East pipeline projects.

"In recent weeks, Mr. Gagnier has been observed providing counsel to Mr. Trudeau on the Liberal campaign plane, and on the Liberal campaign bus," she wrote. "He was without question an active, ongoing participant in the conduct of the campaign."

Gagnier stepped down from his position on Wednesday, shortly after news of the email became public. The Liberals say they have complied with all the rules of the election campaign, and Gagnier decided to do the "ethical and responsible" thing by stepping down.

McGrath suggested the Liberals knew about Gagnier's "activities for some time," but they did not act on that knowledge "until the media and the public found out."

In a separate statement also issued Friday, McGrath suggested the Liberals had known about Gagnier's association with TransCanada.

"The facts of this matter keep changing, and it now seems clear that both the Liberal Party of Canada and TransCanada Corporation knew of Mr. Gagnier's activities for some time," she wrote. "Elections Canada needs to investigate this matter, thoroughly and quickly."

On Friday, Liberal Leader Justin Trudeau said the party was aware of Gagnier's ties to TransCanada, but Gagnier was "not involved in our campaign in the energy sector."

His party also fired back at Mulcair, pointing out that his top strategist -- Brad Lavigne -- was registered as a lobbyist in Ontario during the campaign.

A search of Ontario’s Office of the Integrity Commissioner website appears to show Lavigne arranged a meeting for the Canadian Fuel Association in late September for Hill+Knowlton Strategies.

However, Lavigne told The Canadian Press the listing is a mistake, that he deregistered as a lobbyist, and he quit Hill+Knowlton last May.

Trudeau said Friday that all parties draw in volunteers from "across the country," and a potential prime minister "should surround himself with extraordinary backgrounds." He stressed that when Gagnier's "inappropriate" email came to light, "there were immediate consequences."

Conservative Leader Stephen Harper said Gagnier's behaviour demonstrates the "culture" of the Liberal Party. "There is no other party in this election that is accused of the thing the Liberal Party and Mr. Gagner have done," Harper said, at a campaign event in Quebec City. "It is the old culture of the sponsorship scandal."

None of the allegations against Gagnier, the Liberals or TransCanada have been proven in court.

With files from CTV's Richard Madan and The Canadian Press