The Conservative government was warned last summer that working with the Afghan secret police would lead to allegations Canada condoned abuse and that Canadians could face legal liability for complicity in torture.

In this July 2009 file photo, a man Afghan authorities suspect of insurgency-related activities is interrogated during a joint Canadian-Afghan army patrol in the Panjwaii district of Kandahar province. (Colin Perkel/Canadian Press)

The information, contained in a candid top-level government memo shared with CBC News, shows that officials were worried that Canada's relationship with the Afghan National Directorate of Security was risky — and possibly illegal — even while the government was defending it.

The document warns that the directorate, or NDS, is so secretive, even Canada and its allies are in the dark about much of what it does.

The NDS has wider powers of arrest and detention than most intelligence agencies, the memo says, and as a result, "there is considerable scope for the use of improper methods." Engaging with the NDS "entails a degree of risk to Canadian interests," it adds.

The document doesn't detail those risks specifically, but human rights lawyer Paul Champ said he has an idea of what they are.

Champ is the lawyer at the centre of several investigations into the alleged abuse of Afghan detainees. He said the NDS can't be trusted with detainees transferred into its custody by Canadian soldiers, and the Conservative government is well aware of this.

"Make no mistake, the methods of the NDS are well known," Champ told CBC News. "It's electric shocks, it's pulling out toenails, it's beating people with chains, it's hanging them for days. So when someone says abuse, that's a euphemism for torture."

The memo's assessment of the directorate seems to make use of that euphemism. It cautions Canada ought to be concerned about its longstanding relationship with the secret police.

"Canadian partnership in NDS projects without prior insight into its methods runs the risk of appearing to condone human rights abuses and acts which would be illegal under Canadian law," the document states.

'More robust' transfer agreement fixed problems: Tories

Government officials admit that Canada has used the fruits of NDS intelligence-gathering. Brig-Gen. Denis Thompson, former commander of the Canadian mission in Afghanistan, told a parliamentary committee last week that his assessment of the NDS in fighting the insurgency "is that they were a very valuable partner, and I mean, we acted on the intelligence we received from the NDS."

But the government says that after allegations of torture of Afghan detainees first came to light in April 2007, Canada acted quickly to fix its transfer agreement with the Afghans.

In an email to CBC News, Dimitri Soudas, spokesman for Prime Minister Stephen Harper, vigorously defended the "more robust" agreement the Conservatives brought in, saying Canadian officials have conducted 210 prison visits since its implementation.

"Canadian soldiers, corrections and police officers, aid workers and diplomats continue to put their lives at risk every day in Afghanistan to support and improve human rights and to build a better future for all Afghans," Soudas wrote.

Under the 2007 agreement, the government gained access to the prisons of the NDS and had Canadian monitors follow up on the condition of detainees. This scrutiny is supposed to ensure that detainees are protected from being tortured.

Soudas said Canadian officials take their international human rights obligations seriously and Canadian soldiers only transfer prisoners to Afghan authorities if the Canadian commander is "satisfied that there are no substantial grounds for believing that there exists a real risk that a transferred prisoner will be subjected to torture or other forms of mistreatment."

"If those conditions are not met, the Canadian commander can halt transfers — as he has done so in the past," he wrote.

Battle over documents

A special Commons committee on the Afghanistan mission has been investigating the issue for months and has heard the government had clear warnings about torture in the first half of 2007 but continued to transfer detainees into Afghan custody.

Last November, the committee heard bombshell testimony from former top diplomat Richard Colvin, who alleged that all prisoners handed over by Canadian soldiers to Afghan authorities were likely subsequently abused and that government officials were well aware of the problem. Government and military officials have vehemently denied Colvin's allegations.

Opposition parties have accused the Harper government of using the recent two-month prorogation of Parliament to hinder the committee's work and avoid potentially embarrassing questions on the Afghan detainee affair.

The opposition passed a motion in the Commons three months ago demanding the government provide uncensored versions of all documents related to the transfer of Afghan detainees.

But the government has insisted it is legally bound by security and public safety concerns and is working with Parliament to provide "all legally available" documents as quickly as it can.