A parliamentary committee will hear from strong supporters and vocal critics of the government's anti-terrorism bill, but not from four former prime ministers who have decried the lack of increased oversight in the legislation.

Bill C-51 would beef up the powers of the Canadian Security Intelligence Service, criminalize the promotion of terrorism and provide the RCMP with new powers of preventative arrest. But critics charge it goes too far and risks ensnaring environmentalists and natives in the fight against terrorism.

The public safety committee of the House will hear from 50 witnesses between March 9 and 31 as part of its study of the bill, starting with Public Safety Minister Steven Blaney and Justice Minister Peter MacKay. The 48 remaining slots will be filled from a list of 70 potential witnesses, based on their availability.

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According to the list obtained by The Globe and Mail, witnesses will come from a wide range of society, including government, academia, law enforcement and various non-governmental organizations.

For example, the committee could hear from former public safety ministers (Liberal Anne McLellan and Conservative Stockwell Day), current and past members of the Security Intelligence Review Committee, current and past privacy commissioners, and retired judges John Major and Louise Arbour.

The list of potential witnesses includes fierce critics of C-51, namely Maher Arar, who was tortured in Syria after being flagged as a security risk in Canada, and law professors Kent Roach and Craig Forcese.

The committee, on which Conservative MPs hold a majority, also wants to hear from Canada's international allies, including the Secretary of the U.S. Department of Homeland Security, Jeh Johnson, and New Zealand Attorney-General Chris Finlayson.

Other potential witnesses include officials from NGOs such as Greenpeace Canada, the Ukrainian Canadian Congress, the Council for Muslims Facing Tomorrow, the Canadian Muslim Lawyers Association and the B.C. Civil Liberties Association.

However, the NDP has failed to persuade the committee to call former prime ministers Joe Clark, John Turner, Jean Chrétien and Paul Martin, who have written an open letter criticizing the lack of oversight of Canada's spy agencies in the new legislation.

NDP MP Randall Garrison said he is concerned the committee will only have two hours with Mr. Blaney, Mr. MacKay and their officials, including RCMP Commissioner Bob Paulson and CSIS director Michel Coulombe.

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"What we have seen so far from both ministers is a tendency to wave the fear flag rather than discuss the contents of the bill," said the NDP's public safety critic. "With a two-hour session with the ministers and all their officials, we are not likely to get very far."

Mr. Garrison said the committee scheduled evening hearings in the week of March 23, but feels that more time could have been spent studying the legislation. The Conservatives initially wanted to hold only three days of hearings on the matter, but added six more days after the NDP launched a filibuster.