Opposition MPs and civil rights groups say they are worried that new anti-terror legislation does not boost oversight of Canada's spy agency, but the Conservative government is dismissing their concerns.

Several MPs voiced their unease this week with legislation that would give the Canadian Security Intelligence Service powers to actively disrupt terrorist threats. The new rules would also make it easier for police to control the movements of terror suspects and to detain them longer without warrant.

"This Parliament must not allow the Conservatives to turn CSIS into a secret police force," Green Party Leader Elizabeth May said during the daily House of Commons question period Monday.

NDP Leader Thomas Mulcair said other countries, like the U.S. and the U.K., have "serious oversight" over their intelligence agencies, "and that's done by elected officials."

During question period Tuesday, Liberal Leader Justin Trudeau asked Prime Minister Stephen Harper why the anti-terror bill does not include parliamentary oversight of CSIS.

“We already have a rigorous system of oversight on our national security police agency,” Harper said. “It functions very well.”

Public Safety Minister Steven Blaney also insisted that the government-appointed Security Intelligence Review Committee, which oversees CSIS, is “well-established” and doing a good job.

“Canada is at war with terrorists and jihadists,” Blaney told the House of Commons Tuesday, speaking in French. He said CSIS does important work and he has full confidence in civilian oversight of the spy agency.

But some experts fear that, with little oversight and expanded powers, CSIS operations may infringe on civil rights.

"When we are dealing with civil liberties and infringement by these secret government agencies, which they are now, CSIS is becoming like a secret police," said lawyer Paul Cavalluzzo, who was the senior commission counsel at the Maher Arar inquiry.

"We do need effective oversight," he said.

Some Muslim leaders also expressed concern about the language Prime Minister Stephen Harper used when he presented the anti-terror bill on Friday.

"It doesn't matter what the age of a person is, or whether they're in their basement, or whether they're in a mosque or somewhere else," Harper had said. "When you are engaged in activities that explicitly promote or advocate terrorism, that is a serious criminal offence no matter who you are."

The National Council of Canadian Muslims and the Canadian Muslim Lawyers' Association took offence Monday at the reference to mosques and Mulcair called it a "form of Islamophobia."

A spokesperson for Harper said the prime minister did not say that all radicalization occurs in mosques, but that it could happen anywhere.

With a report from CTV's Ottawa Bureau Chief Robert Fife and files from The Canadian Press