Toronto, Canada - Canada must launch a public inquiry into the alleged torture of hundreds of Afghan detainees during the country's military mission in Afghanistan, a group of human rights advocates, legal experts, politicians and diplomats has said.

Detainees were transferred from the Canadian military to Afghan authorities "notwithstanding very clear and credible risks of torture", the group said in an open letter, sent to Prime Minister Justin Trudeau earlier this week. 

"No one knows exactly how many detainees who were in Canadian custody were tortured, disappeared or died under Afghan custody ... partly due to the cloud of secrecy the previous government relentlessly maintained over this matter," the letter said.

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Canada's military involvement in Afghanistan began in 2001 and formally ended in 2014, with more than 40,000 troops deployed - the largest Canadian military operation since World War II.

Canadian diplomats in Afghanistan described instances of detainees being beaten with electric cables, rubber hoses and sticks, or being threatened with execution or sexual assault, among other punishments, the letter's 41 signatories said.

Alex Neve, head of Amnesty International Canada and one of the letter's signatories, said a public inquiry would allow Canadians to finally understand what took place in Afghanistan - and prevent a similar situation from happening again.

"We have never understood who made the orders, on what basis, [and] why, even as more evidence came to light that the torture risk was indisputable, the determination to stick with the policy only deepened," Neve told Al Jazeera.

"Unless we probe and examine why this came to pass ... then there's every possibility this may simply be repeated. And we cannot afford that possibility."

In response to the report, Jordan Owens, press secretary for Canada's defence ministry, told Al Jazeera that "when it comes to situations of armed conflict, members of the Canadian Armed Forces receive a rigorous pre-deployment training with respect to the Geneva Convention and international law".

Rideau report

Canada transferred detainees into the custody of Afghan National Security Forces (ANSF), most frequently the National Directorate of Security (NDS), a recent Rideau Institute report on the torture of Afghan detainees said.

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The North American country originally had no ability to monitor the detainees' conditions post-transfer, but a subsequent deal later granted its diplomats the ability to visit detainees.

"After Canadian diplomats started monitoring the conditions of detainees, they started discovering many instances of abuse," Omar Sabry, the author of the report, told Al Jazeera on Thursday.

"So these were incontrovertible cases of people who were known to have been transferred by Canada and who said themselves in interviews that they were tortured."

Sabry said that the transfers of detainees continued even after Canadian officials discovered instances of abuse, in violation of international law.

'Complicity in torture'

In 2009, whistleblower Richard Colvin, a Canadian diplomat who served in Afghanistan for 17 months, described Canada's "complicity in torture", as well as indifference and obstruction from higher-ups when he raised concerns.

"According to our information, the likelihood is that all the Afghans we handed over were tortured. For interrogators in Kandahar, it was standard operating procedure," Colvin told a parliamentary committee at the time.

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Canada's previous Conservative government, under former Prime Minister Stephen Harper, fought efforts to investigate the allegations. At the height of the scandal in 2009, Harper shut down the parliament for two months.

Neve, of Amnesty International, said senior members of the current government in Ottawa showed support for an inquiry when they were in opposition in parliament.

"Our expectation is that the government will agree that this is something that needs to happen."

The open letter came a few days before Ottawa must respond to a petition calling for an independent commission of inquiry into the events.

That petition, which the government must address by June 16, garnered 727 signatures from people across Canada.

Source: Al Jazeera