NDP Leader Tom Mulcair had earlier avoided commenting on the so-called charter of Quebec values, calling it a trial balloon.
A leaked media report — which the Parti Quebecois government has not denied — said the charter would ban public employees from wearing religious head coverings and other religious symbols at work.
Mulcair now says he opposes anything that might scapegoat certain kinds of Quebecers.
"I don't want to see scapegoating, particularly of Muslim women," Mulcair told reporters on Parliament Hill on Monday.
"That seems to be one of the particular targets here. So we'll wait and see what's in it."
Parti Quebecois Leader Pauline Marois says a charter of values will unite Quebecers. A Leger Marketing poll released this week suggests a majority of Quebecers support the idea behind such a charter, although nearly half also think it will create divisions.
Mulcair and most of his caucus come from Quebec ridings — a fact that might explain his reluctance to come out too strongly against the proposals.
He says he won't support legislation that goes against the recommendations of a 2008 provincial commission on accommodating cultural communities.
That commission recommended that judges, police officers and others in the legal or law enforcement arenas be barred from wearing religious symbols, but exempted teachers, doctors and other public servants.
"If there's anything in what Madame Marois is proposing that goes against that, then for us it's an absolute non-starter and we will stand up strongly against it," said Mulcair. "But we haven't seen the text of anything yet. So rather than going against something that we haven't seen, we'll simply state the principle."
Liberal Leader Justin Trudeau has been more direct in his criticism of the secularization charter, saying it would promote fear of others and is unworthy of the province.
So far, the Conservative government has said very little about the issue, calling it a provincial matter.
One Tory MP who represents a Calgary riding called for the rejection of what he called an intolerant policy position.
“It is extremely disappointing for me to see how the Parti Quebecois is attempting to undermine dearly held Canadian values,“ Devinder Shory said in a statement, noting that he lived in Montreal when he first moved to Canada.
“The proposed charter will lead to a more intolerant society within Quebec, and will negatively impact the many Quebeckers who chose to contribute positively to society through their hard work in the public service.”
The Prime Minister's Office and cabinet members have still avoided weighing in.
But senior figures in the government did oppose a Quebec soccer league's ban on turbans earlier this year. The Tories also speak out frequently on protecting religious freedom internationally — Foreign Affairs John Baird underlined that distinction Monday.
"I think one of the things that we made very clear when we launched the office of religious freedom within the Department of Foreign Affairs was that my mandate is strictly outside of the country," Baird told reporters in Toronto.
"So I'm going to repeat that obviously I'm a big believer in freedom, I'm a big believer in freedom everywhere, but the mandate that I have is in Foreign Affairs."
The Quebec government has not formally released the details of the proposed charter, but Marois trumpeted it over the weekend.
"We're moving forward in the name of all the women, all the men, who chose Quebec for our culture, for our freedom, and for our diversity," she said Sunday at a gathering of young PQ members in Quebec City.
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