The Conservatives have agreed to triple the number of parliamentary hearings into the government's anti-terrorism legislation under pressure from an NDP filibuster for additional expert testimony on Bill C-51.

The Conservatives voted on Thursday to hold nine meetings on the matter at the public safety committee of the House between March 9 and 31, up from an initial proposal of three meetings. This will bring to 50 the number of witnesses who will speak on the proposed legislation, including Public Safety Minister Steven Blaney and Justice Minister Peter MacKay.

The government is arguing it must move quickly on the matter, as reports continue to come in of Canadians travelling to the Middle East to join Islamic State extremists. The latest case involves six young Montrealers who recent left the country and are thought to have become radicalized.

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Bill C-51 would beef up the powers of Canada's spy agency, criminalize the promotion of terrorism and make it easier to stop Canadians from joining terrorist groups abroad.

The NDP has been leading the opposition to the proposal, arguing it offers unnecessary powers to law-enforcement agencies and puts law-abiding citizens at risk of being ensnared in the anti-terror fight.

During Question Period, Prime Minister Stephen Harper slammed the Official Opposition for putting up a fight to obtain greater scrutiny of the legislation.

"Now is not the time for the NDP agenda of attacking the police and the security agencies," Mr. Harper said. "Now it is time to take on the terrorists, and that is what we are doing."

NDP MPs were filibustering the committee meeting in a bid to force the Conservatives to agree to hold 25 meetings in March. The NDP argued the Conservative schedule would cram too many witnesses at each hearing, leaving them only 20 minutes on average to make their case.

"We are not asking for delay, we are asking to do more work on this bill," NDP MP Randall Garrison said. "We believe it is important to get this right."

The NDP will now be able to invite about one third of the witnesses at the committee, with NDP MP Rosane Doré Lefebvre stating the list will include retired judges, members of First Nations and retired law-enforcement officials.

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She said the fact the Conservatives agreed to increase the number of hearings was a "small victory" for the NDP. She now hopes the government will listen to the experts and make changes to the legislation.

"It's difficult to pass amendments with the Conservative government," she said. "For anything to happen, it must come from both sides. We need to come to a consensus that this is not the time for politics but a serious matter of national security."

The NDP has already stated that it will vote against C-51 unless it wins substantial amendments to the legislation.

The chair of the public safety committee of the House argued on Thursday it was time to study the legislation, instead of debating the number of witnesses that will be heard.

"Time is of the essence," said Conservative MP Daryl Kramp. "I don't want Rome to burn when Nero fiddles. The terrorism threat is real."

Mr. Harper urged the committee to quickly complete its study of Bill C-51 on Thursday, noting the legislation is "strongly supported by Canadians."