OTTAWA -- Liberal Leader Justin Trudeau and his Bloc Quebecois opponent Yves-Francois Blanchet clashed sharply over Quebec's controversial secularism law during a French-language debate Wednesday night.

The province passed its secularism law, Bill 21, in June that prohibits public servants who are deemed to be in positions of authority -- teachers, judges and police officers, for example -- from wearing religious symbols.

That includes hijabs for Muslim women and yarmulkes for Jewish men.

The federal leaders have trod carefully on Bill 21, a reflection that the law is extremely popular in vote-rich Quebec.

Previously on the campaign, Trudeau kept the door open to a future intervention by the federal government, but has said that would be "counterproductive" now while it is the subject of a Quebec court challenge.

On Wednesday night, Trudeau appeared more forceful on that point, as Blanchet drew him into a discussion on the importance of protecting minority rights -- including those of francophones outside of Quebec.

"My personal perspective is a free society should not legitimize discrimination, but I respect that it's a conversation that's happening in Quebec for the moment. I am not going to shut the door, as the federal government, on defending the rights of people, whether it's the rights of LGBT people, the rights of women, or the rights of minorities," Trudeau said.

"I think it's important for the government to defend, for instance, the rights of francophones outside Quebec."

Blanchet suggested Trudeau would become more forceful in his opposition to Bill 21 if he wins the Oct. 21 election.

"I have an enormous problem with the possibility that the money of the same Quebecers who elected people to the National Assembly, who voted for a law in the National Assembly -- that they'll be sending money to Ottawa, that after Oct. 21 will support groups that will encourage and support efforts against the law."

Trudeau doubled down on his commitment to protect minority rights.

"To me, the big threat that we see to the secularism of the state is extreme right-wing groups that push an agenda that's anti-women, anti-abortion, anti LGBT, and that's coming back," said Trudeau.

Blanchet fired back with a pair of pointed questions:

"Are you saying the 70 per cent of Quebecers who support this law are sympathetic to groups of the extreme right?" he asked. "Doesn't the Quebec nation have the right to express its own values in its own parliament without seeing its own tax dollars put to fighting it?"

Quebec Premier Francois Legault, who has branded his Coalition Avenir Quebec as nationalist, has said the law reflects the will of the province's French-speaking majority and he has warned the federal leaders to steer clear of the issue during their campaigning.

The Quebec government also invoked the notwithstanding clause in the Constitution to avoid having the law struck down as a violation of the Charter of Rights and Freedoms.

Two organizations have launched a legal challenge of the new law all the same.

A recent Quebec Superior Court decision rejected a request for a stay of certain provisions of the law. The National Council of Canadian Muslims and the Canadian Civil Liberties Union are appealing that decision. A hearing is set for Nov. 26 before the Quebec Court of Appeal.

Conservative Leader Andrew Scheer and the NDP's Jagmeet Singh have criticized the law but have said they would not intervene to challenge it.

During the debate, Singh displayed his distaste for Bill 21. "It's a law that discriminates. I oppose laws that discriminate."

Singh is a practising Sikh who wears a turban.

Earlier Wednesday, Singh had a brief exchange with man at a downtown Montreal farmers' market who told him he should "cut off this turban" so he would "look like a Canadian."

"I think Canadians look like all sorts of people," Singh replied. "That's the beauty of Canada."

The law has caused ripples outside Quebec.

On Monday, Calgary city council unanimously passed a motion formally opposing the Quebec law.

Mayor Naheed Nenshi said it was important for the city to take a stand, and to tell its own citizens of minority faiths that council stands for them and by them.

He says he will forward Calgary council's motion to all mayors across the country.

This report by The Canadian Press was first published Oct. 2, 2019.