Defence Minister Peter MacKay says he wasn't aware of warnings authored by a Canadian diplomat that prisoners in Afghanistan faced the risk of being tortured if transferred to local authorities.

"I have not seen those reports in either my capacity as minister of National Defence or previously as minister of Foreign Affairs," he told The Canadian Press.

MacKay was responding to an affidavit that diplomat Richard Colvin filed to the Military Police Complaints Commission on Wednesday, which said that government officials knew of the risks because he personally warned them in writing in 2006.

Colvin -- who is now an intelligence officer with the Foreign Affairs department -- said in his written statement that he filed two reports in 2006 that examined potential problems with the handover of prisoners by the Canadian military to the local authorities.

"Judging these problems regarding Afghan detainees to be serious, imminent and alarming, I made investigations and detailed my findings formally in my reporting from the PRT," he wrote in the affidavit.

His statement contradicts earlier assurances by Prime Minister Stephen Harper and other high-ranking officials that they had not received any credible reports from Canadian officials about prisoner abuse.

Cabinet ministers had also assured the public that the opposition was misled by Taliban propaganda, and that in fact, the government has not received a credible allegation of prisoner abuse.

That revelation has resulted in opposition calls for an official public inquiry into issue.

However, the Canadian government said that when the allegations came to light in the spring of 2007 that they had never received any prior warning about the risk of torture.

The content of the first report is still covered by national security. Colvin said the second report gave specific findings that "dealt with two issues, one of which concerned the risk of torture and/or actual torture of Afghan detainees."

But opposition MPs say the government may be hiding something.

"Peter Mackay and the prime minister must come forward and tell Canadians exactly what they knew, and when they knew it. That is the clearest, fastest, and most honest way to proceed," said NDP defence critic Jack Harris on Thursday.

The NDP is now calling for a public inquiry into the issue.

The Liberals echoed those concerns and said that the government is attempting to "muzzle" one of its own diplomats.

"The government is obstructing justice by not co-operating with the Military Police Complaints Commission's request to hear from Canadian diplomat Richard Colvin," said Liberal Defence Critic Ujjal Dosanjh in a media release.

"As a result of their stonewalling, the commission's investigation is now shut down for at least six months."

Commissioner Peter Tinsley agreed to adjourn the hearing but blasted the Canadian government for stonewalling the inquiry by withholding the requested documents.

Government officials say they are in the midst of censoring documents about the issue for national security, but critics say they're taking too long to get the job done.

Meanwhile, Freya Kristjanson, a lawyer with the Canadian Military Complaints Commission, told Canada AM that while the government has said it's co-operating with the commission, it has not turned in any documents since March, 2008.

"This commission has not received a single new document (sic) despite repeated assurances that the government would be producing the documents both in the House and by their lawyers directly to the commission," she said in an interview from Ottawa. "The government has simply failed to deliver any documents."

"If the government co-operates with a body established by Parliament within its mandate and gives the commission documents and access to witnesses then Canadians will know what happened," she added.

"The commission absolutely will protect valid national security claims but the problem is the government is not co-operating or expediting the vetting of those national documents so that we can proceed with this hearing," she said.

The lawyer's comments come a day after the commission was adjourned for at least six months to deal with arguments over the inquiry's jurisdiction.