Prime Minister Stephen Harper has defended the role of Canada's spy service in the questioning of Afghan prisoners, saying the agency respects its "international obligations at all times."

Prime Minister Stephen Harper speaks during Monday's question period in the House of Commons in Ottawa. (Sean Kilpatrick/Canadian Press)The prime minister's defence of the Canadian Security Intelligence Service came in response to fresh calls from opposition leaders for a public inquiry into Afghan detainee transfers amid media reports detailing CSIS's previously undisclosed role in the interrogation of suspected Taliban fighters.

During Monday's question period, Harper chided the opposition for unfairly accusing "public servants" of concealing documents related to the Afghan detainee affair and said his government is providing further assurances with the appointment of retired Supreme Court Justice Frank Iacobucci to review the documents.

Liberal Leader Michael Ignatieff, who called the media reports "disturbing," said the government "lacks all credibility" on the Afghan detainee file and questioned how Iacobucci could do his job properly with such an unclear mandate.

"They have withheld uncensored evidence to Parliament. Now, they've asked the justice to decide what evidence Parliament should and shouldn't see," Ignatieff told the House. "Why not give Canadians the truth, why not appoint a full public inquiry, to get to the bottom of this sorry affair?"

Liberal MP Ujjal Dosanjh, a member of the special House committee on Afghanistan, asked the prime minister whether the government conducted a deliberate policy of rendition and outsourcing of torture of Afghan detainees for extracting additional information.

Harper did not shed any light on the level of CSIS participation in Afghan interrogations, but insisted Iacobucci will give a public report on his review of all federal documents.

"I hope if the honourable member does not trust the government, if he doesn't trust the Canadian Forces, doesn't trust the foreign service or anybody else, maybe he can trust Justice Iacobucci to review the documents," the prime minister told the Commons.

CSIS 'should not be the CIA': Layton

NDP Leader Jack Layton accused the Conservatives of "playing for time" and denying a parliamentary order to provide the documents in unredacted form to the Afghanistan committee, which was conducting hearings into the allegations of detainee torture at the hands of Afghan intelligence officials prior to Harper proroguing Parliament.

"CSIS is not and should not be the CIA," Layton said, an apparent reference to the U.S. spy agency's controversial extra-judicial renditions of suspected al-Qaeda and Taliban operatives and leaders in recent years.

Harper replied that CSIS "is not the CIA, but is Canada’s premier intelligence service and respects its international obligations at all times."

The allegations of detainee abuse triggered national debate last year after heavily redacted versions of the military and diplomatic documents were made public following an access to information request filed by University of Ottawa law professor Amir Attaran.

The documents revealed the Canadian military was not monitoring detainees who had been transferred from Canadian to Afghan custody. It was later alleged that some of those detainees were being mistreated.

Late last week, Attaran alleged that the uncensored documents suggest that Canadian officials intended some prisoners to be tortured in order to gather intelligence. If the allegation is true, such actions would constitute a war crime, he argued.

Citing heavily censored witness transcripts filed with the Military Police Complaints Commission, The Canadian Press reported CSIS spies began working side-by-side with a unit of military police intelligence officers as the Afghan war spiralled out of control in 2006.

In response to the CP report, Defence Minister Peter MacKay acknowledged the military has "relied heavily on other departments, including CSIS" to counter the severe threat to Canadian troops in Afghanistan.

In his appearance before the Afghanistan committee last November, Richard Colvin, a former top Canadian diplomat in the Afghan mission, testified that all detainees transferred by Canadians to Afghan prisons were likely tortured by Afghan officials. He also said that his concerns were ignored by top government officials and that the government might have tried to cover up the issue.

The government and military commanders have vehemently denied Colvin's claims.

With files from The Canadian Press