Mulcair said in French on Wednesday that emphasizing the niqab issue was the latest from the Conservatives' "bag of tricks" in what he added has become a "truly toxic" campaign.

He noted that while it's an emotional issue for some, it only directly affects a small number of people who are in a very specific situation.

"But it stirs up fear of the unknown," Mulcair said in an effort to position himself above the fray.

"By focusing on what divides us, negative discourse that derails the election-campaign debate distracts us from what's essential."

On the niqab issue, the NDP is also facing attacks from the Bloc Quebecois, which it nearly wiped off the province's electoral map in 2011. The Bloc has argued that the constitutional notwithstanding clause could be used to supersede the Charter of Rights in order to ban face coverings at citizenship ceremonies.

"I understand that many view the niqab as a symbol of the oppression of women," Mulcair said.

"And on that, let me be clear: No one has the right to tell a woman what she must — or must not — wear."

Mulcair continued by saying the country should reach out to oppressed women hoping to become citizens.

"It is not by depriving them of their Canadian citizenship and their rights that we can help them," he said.

At a news conference earlier in the day, Mulcair faced several questions in both French and English on the niqab issue.

He was also asked whether he would support a Conservative minority government.

"There isn't a snowball's chance in hell," he said.

"There's no likelihood that the NDP would ever, under any circumstances, be able to support Mr. Harper, his divisive politics, his backward economics that have left 400,000 manufacturing jobs disappear over the last few years."

That echoed a pledge from Liberal Leader Justin Trudeau, who said Tuesday there are "no circumstances" in which he would support Harper staying on as prime minister with a minority.

In the morning, Mulcair joined Montreal Mayor Denis Coderre for a wide-ranging news conference, which included a reiteration of an NDP promise to reverse Canada Post's plan to phase out door-to-door mail delivery.

That was welcome news for Coderre, who last month used a jackhammer on the concrete base of a community mailbox that the mayor said was installed without consultation.

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By Andy Blatchford, The Canadian Press