Nearly half of the Afghans captured by Canadian troops in 2010 and 2011 had no links to the Taliban and were illegally held far longer than Ottawa has publicly acknowledged, military police said Wednesday.

In an open letter published by La Presse newspaper, the police officers called for accountability for the wrongful detention and mistreatment of Afghan farmers and others who "found themselves in the wrong place at the wrong time in the middle of urban warfare."

A military police complaints commission launched an investigation last November into the allegations first raised by an interpreter and Canada's former ambassador to Afghanistan. It continues.

The police officers said they want the true version of events to be made public and for senior officials to testify in front of the complaints commission.

The police officers who offered corroborating evidence said they witnessed "reprehensible acts" committed against prisoners at the Canadian base at Kandahar province.

Military police were ordered to "terrorize" the detainees to make them more amenable to interrogation, they said.

Detainees, they said, would be awakened in the middle of the night, visibly "frightened and in a panic" to find up to 50 soldiers in their cell.

Almost half would turn out to be villagers or farmers with no ties to the Taliban insurgency, and were released.

But this came only after being held for up to two months, they said, far longer than the average 48-96 hours of detention claimed by the Canadian government of the day.

Canada also had a secret deal with Afghan forces who would claim to have the detainees in their custody, they added.

"Almost 50 percent of the prisoners held by military police were just people like you and me, husbands, fathers, farmers, who had nothing to apologize for. Why and how could this contempt for our laws and Canadian values have occurred," the police officers said in the letter.

The mass roundups, they concluded, were motivated by a desire to kill or incarcerate the largest possible number of Taliban and bring a swift end to the conflict in which 162 Canadians died and more than 2,000 were wounded.

The wrongful imprisonment, however, just aggravated tensions with local villagers, causing bitter resentment against the Canadian troops, they said.

In parliament, Defense Minister Harjit Sajjan said: "We take this very seriously. Our government stays committed to upholding our Canadian and international law obligations.

"My officials will be looking into these allegations," said Sajjan, who deployed to Afghanistan in 2006, 2009 and 2010.

The opposition New Democratic Party called for a public inquiry.

"What we have here is a potential stain on Canada's international reputation through possible violations of international law and also a stain on the reputation of all those Canadians who went there and served in good faith. So we need a full independent public inquiry to determine what actually happened," NDP MP Randall Garrison told reporters.