OTTAWA–A senior diplomat delivered a series of explosive allegations to a rapt House of Commons committee Wednesday, telling MPs that Afghan prisoners transferred by Canadians to local authorities in Kandahar were likely all tortured – while high-level officials in Ottawa looked the other way.

"Canada ... cloaked our detainee practices in extreme secrecy," Richard Colvin, a Washington-based intelligence officer, said in long-awaited testimony to a special parliamentary committee.

"Our detainee practices (were) unCanadian, counterproductive and probably illegal."

Colvin, the second-ranked Canadian diplomat in Afghanistan in 2006 and 2007, said he tried repeatedly to raise concerns with senior military and government officials, to no avail.

Using a calm, controlled diplomatic cadence, he challenged three years of assurances by the Conservative government that no evidence existed of abuse of prisoners captured by Canada.

He said Canadians took far more prisoners than their NATO allies in Afghanistan, many of them innocent people swept up in the chaos of war, and he charged that the policy had taught Kandaharis to fear the foreign troops and had set back the Canadian effort in the region.

"According to our information, the likelihood is that all the Afghans we handed over were tortured," said Colvin, the former political director of the provincial reconstruction team in Kandahar city. "For interrogators in Kandahar, it was standard operating procedure."

He also said that when the Red Cross wanted to look into the treatment of detainees turned over by the Canadian troops, the Canadian Forces wouldn't take their calls.

Colvin had to fight for his afternoon in the spotlight, an appearance the Harper government tried to block. And Conservative MPs attacked his credibility in the committee room.

Colvin named those who were warned about the prisoner treatment and did not act, including now retired chief of defence staff Gen. Rick Hillier; David Mulroney, former deputy minister of the Afghanistan Task Force in the Privy Council Office; and Margaret Bloodworth, Prime Minister Stephen Harper's national security adviser.

Colvin said he had no knowledge whether the matter was brought to the attention of then-Foreign Affairs Minister Peter MacKay.

In his recently published memoir, Hillier brushed off allegations the military was complicit in torture as "bull----."

Colvin said Canada took six times as many detainees as coalition partner Britain and 20 times as many as the Netherlands, and had no way to track their whereabouts.

He said warnings that they were being tortured with electricity, extreme temperatures, knives, open flames, and even sexually abused, were ignored.

He said Canada relied on two human rights groups – the Afghanistan Independent Human Rights Commission and the International Committee of the Red Cross – to monitor the well-being of detainees after transfer.

"Unfortunately the AIHRC had very limited capacity and in Kandahar were not allowed into the NDS (National Directorate of Security) prisons ... and unfortunately were quite useless," he said.

Colvin noted that the Red Cross was "also no good for us as monitors" because under its rules once a detainee is transferred the Red Cross can only inform the Afghan authorities about abuse.

He said, unlike the British, Canada was extremely slow to inform the Red Cross when detainees were transferred to the Afghans, in some cases taking months.

"Instead of winning hearts and minds, we caused Kandaharis to fear foreigners," he said.

Colvin said when the Red Cross wanted to look into the treatment of detainees turned over by Canadian troops "the Canadian forces in Kandahar wouldn't take their phone calls," adding that Canada's military even refused to tell NATO officials the number of detainees.

"In practice, the information was being concealed ... from the Canadian public," he said.

Warnings first delivered in spring 2006 were ignored by senior Canadian Forces and government officials for a year until newspaper reports brought the allegations of mistreatment to light.

After that, Colvin said, diplomats were instructed not to keep written records of any talk of torture by their higher-ups in Ottawa.

Colvin, now an intelligence officer at the Canadian Embassy in Washington, worked in Afghanistan for the foreign affairs department in 2006 and 2007. He started in Kandahar and later moved to Kabul, where he was second in command at the Canadian Embassy. In both jobs, Colvin visited detainees transferred by Canadian soldiers to Afghan prisons.

Colvin said in May 2006 he and others "began informing Ottawa" through written reports and verbal briefings to senior officials in both the foreign affairs department and the Canadian Forces "about the grave deficiencies in our detainee practices and grave consequences."

"At first we were mostly ignored, but by April 2007 we were receiving written messages from the senior Canadian government co-ordinator for Afghanistan to the effect that we should be quiet and do what we were told," he said.

Colvin said that was followed by a phone call from the assistant deputy minister of foreign affairs "suggesting in future that we should not put things on paper but instead use the telephone."

He said in May 2007 detainee reports began to be censored, "with crucial information removed," and later that summer "we could no longer write that the security situation in Afghanistan was deteriorating even though everyone knew that it was."

Colvin testified the Conservative government has tried to block him from testifying before a Military Police Complaints Commission hearing on detainee treatment by denying him legal representation and stopping him from accessing some of the reports he wrote while stationed in Afghanistan.

Conservative members of the committee attacked his credibility and even suggested he was playing into the hands of the Taliban by undermining Canada's military effort in Afghanistan.

"This entire exercise of attempting to draw a link between the Canadian Forces and prison treatment without a shred of evidence is playing right into the hands of the insurgents," Tory MP Cheryl Gallant (Renfrew-Nipissing-Pembroke) said.

Amir Attaran, a University of Ottawa law professor who has challenged the government's detainee policy in federal court, said Colvin's testimony opens up a "large number of issues" relating to past court challenges that have all been dismissed.

He said the government should have put forward a number of the diplomatic memos Colvin wrote relating to detainee policies in court, but never did so.

It's too early to say, though, what the legal implications may be of Colvin's revelations, Attaran said.