"We will strongly defend the fundamental Canadian freedom and association against any effort to encroach upon those fundamental constitutional rights," said Jason Kenney, Canada's minister for multiculturalism.
Quebec's opposition Liberals have criticized the plan, except for the provision banning people from covering their faces while providing or receiving state services.
Liberal Leader Philippe Couillard called the law a "direct attack" on the rights and freedoms of all citizens that threatens to fracture Quebec society.
The Coalition party, which holds the swing vote in the legislature, said it's open to discussions with the PQ.
Polls suggest Quebec, a primarily French-speaking province with a population of 8.1 million, is deeply divided on the issue. Support is higher outside metropolitan Montreal.
Protests both for and against the proposal have been staged since it was first announced in September.
Thousands of Muslims, Sikhs and Jews have marched through Montreal's streets to denounce what they call an affront on religious freedom. Many have said they would lose their jobs rather than comply with the law.
The law would apply to those who work in public institutions such as daycares, schools and hospitals.
Public institutions would have a year to transition to the new rules, though hospitals and universities could be eligible for an exemption of up to four more years, the PQ said.