The Canadian branch of the human-rights organization says the Parti Quebecois proposal would violate Canadian and international law for infringing on freedom of expression and religion.
The PQ plan announced earlier this month would prohibit public employees from wearing obvious religious symbols, including the hijab.
Amnesty took particular issue with one of the stated goals of the proposed charter — that it would promote equality between the sexes.
"For people, and particularly for women, who might be coerced into wearing a religious symbol, prohibiting them from wearing it will not solve the problem," the group said in a statement.
"The people who had coerced them will still go unpunished, while the people who have been coerced will be punished in a number of ways, such as losing their jobs and hence their right to work and risking becoming isolated and stigmatized in their communities."
The group has voiced concern over Quebec policies before.
In April 2012, Amnesty International denounced former Premier Jean Charest's government for its handling of the student protests over tuition fees. The group called for a toning down of police measures, which it deemed unnecessarily aggressive.
This time, the group said it supports the PQ's efforts promote equality between men and women, but takes issue with its proposed approach.
"Women must not be forced to wear a scarf or a veil, neither by the government nor by individuals. But it is no more acceptable for a law to prevent them from wearing such garb," said Beatrice Vaugrante, executive director of the Canadian branch's francophone wing.
The minority PQ government is expected to table the charter this fall and has suggested it might negotiate with opposition parties afterward.
For now, Premier Pauline Marois appears content to let the debate rage on.
Quebec remains bitterly divided over the issue, with duelling protests over the charter's merits planned for this weekend.
A march against the charter was planned for Saturday in Quebec City, while a pro-charter march is set for Sunday in Montreal.
Meanwhile, a coalition of community groups and prominent Quebecers, including former Supreme Court Justice Claire l’Heureux Dube, is planning to hold a news conference Tuesday in support of the proposal, according to Montreal's Le Devoir newspaper.
A new poll released Saturday found more than half of those surveyed— 52 per cent — were in favour of the plan. But 56 per cent felt the charter's constitutionality should be tested in court.
The Leger-Marketing survey, conducted for the Montreal Gazette, questioned 1,001 Quebecers for the web panel poll between Sept. 17 and Sept. 19. Results are considered accurate within 2.9 percentage points, 19 times out of 20.
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