OTTAWA (Reuters) - Canadian Prime Minister Justin Trudeau on Friday said for the first time he might challenge a decision by the province of Quebec to ban public employees from wearing religious symbols, a stance that could hurt him with voters.

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Quebec holds 78 of the 338 seats in the House of Commons and is crucial to the fortunes of Trudeau’s Liberals and his Conservative rivals, who are both looking to make gains in the predominantly French-speaking province in an Oct 21 election.

The Quebec law - which came into force in June - bars teachers, judges and police officers from wearing overt religious symbols such as hijabs and Jewish skull caps.

The government says the law is necessary to ensure society is secular. Critics charge it is a racist measure aimed at the province’s Muslims.

Trudeau said it would be counterproductive for Ottawa to make a move now, noting court challenges against the law have already been launched in Quebec.

For the first time, though, he made clear a government led by him might make a move in future.

“We’re not going to close the door on intervening at a later date,” he told a televised news conference in the Quebec town of Trois-Rivieres.

“I think it would be irresponsible ... to close the door to intervention, ever, on a matter that does touch fundamental freedoms,” he continued, adding that in a free society people should not allow discrimination to occur.

The issue is highly sensitive for Trudeau, who needs to show Canadians he will stand up for basic human rights while not alienating Quebec voters, who could prove critical in what polls show will be a very tight race.

Conservative leader Andrew Scheer said in a televised debate on Thursday night that if he were elected, he would not challenge the Quebec law.

The new law poses a particular problem for Jagmeet Singh, a practicing Sikh who leads the minority left-leaning New Democrats. His fortunes have plunged in Quebec amid questions over whether voters there would back a man who wears a turban.

Quebec Premier Francois Legault - whose Coalition Avenir Quebec government introduced the bill - on Wednesday warned federal leaders not to intervene.

Like France, which passed a ban on veils, crosses and other religious symbols in schools in 2004, Quebec has struggled to reconcile its secular identity with a growing Muslim population, many of them North African emigrants.