A former senior diplomat with Canada's mission in Afghanistan said he repeatedly warned government officials about allegations of torture of detainees transferred by Canadians to Afghan prisons.

An affidavit by Richard Colvin presented to the Military Police Complaints Commission and made public Wednesday challenges the Conservative government's claim that it received no credible evidence to support allegations of torture.

The commission is examining whether military police officers had a duty to investigate the prisoner transfers after the torture allegations surfaced.

Colvin took up his post as political staff officer at Canada's provincial reconstruction base of operations in Kandahar in April 2006. A month later, Colvin said in his affidavit, he wrote a memo to senior military and Foreign Affairs officials describing what he thought were "serious, imminent and alarming" problems with the handling of detainees by Afghan security forces.

Colvin, who also worked in Kabul, said he wrote about 16 more memos about the issue over the next year and a half.

In one of the memos, Colvin outlined specific allegations of torture made by a detainee transferred to an Afghan prison by Canadian soldiers.

But from the time Colvin arrived in Afghanistan until after he left, the government denied it had any "credible" information that would support allegations of torture.

At the time, Prime Minister Stephen Harper described the published reports as "baseless allegations."

Stockwell Day, who at the time was public safety minister and in charge of Corrections Canada staff in Kandahar, said the abuse reports were "false allegations" and accused the opposition in the House of Commons of believing Taliban propaganda.

The current public safety minister, Peter Van Loan, who was the government House leader in 2007, was even more adamant when he said, on April 29, 2007: "We have yet to see one specific allegation of torture. If they have one, we'd be happy to chase it down."

Canada's inaction a violation of international law: Amnesty

For more than two years, the Military Police Complaints Commission has been investigating what the government knew about the torture allegations and when it knew it.

Paul Champ, a lawyer for Amnesty International, which launched the complaint that led to the commission, said Colvin's affidavit highlights two key questions about the government's handling of detainees.

"No. 1: Canadian diplomats were receiving reports first-hand from prisoners saying that they had been tortured. No. 2: Canadian forces continued transfers throughout that period despite those reports of torture," Champ said.

That is a violation of international law, he said.

NDP defence critic Jack Harris said Colvin's affidavit is likely just the tip of the iceberg.

"We obviously need to get to the bottom of this," Harris said. "What else does Mr. Colvin know? This is simply an affidavit. Obviously, he knows more than what is in this affidavit."

But the commission won't get to hear from Colvin for at least six months. It was forced to suspend the hearings two hours after they began on Oct. 7 after the government filed several motions seeking an adjournment in order to let the courts decide the scope of the investigation.

In his decision to suspend the proceedings, commission chairman Peter Tinsley blasted the federal government for stonewalling, saying that "some of the key lessons of the Somalia experience" when it comes to public accountability "have not been learned."

Tinsley was referring to the disgraced Canadian peacekeeping mission to Somalia in the early 1990s during which a young Somali man was beaten to death by Canadian soldiers.

With files from The Canadian Press