David Mulroney testified Thursday that he was aware of problems in the Afghan prison system but there was no alternative to handing over prisoners. (Pawel Dwulit/Canadian Press)

The government's former senior adviser on Afghanistan denied Thursday that he tried to muzzle senior diplomat Richard Colvin, who alleges that prisoners turned over by the Canadian military to Afghan authorities in 2006-07 were tortured.

"Recent testimony and media coverage have left the impression that I discouraged honest reporting about the situation in Afghanistan, and that I contributed to a situation in which detainees captured by the Canadian Forces were transferred to Afghan authorities without due regard to the risk of torture," David Mulroney testified before a House of Commons committee Thursday.

"This is simply not true."

But David Mulroney did say that he was aware there were problems within the Afghan prison system but that there was no alternative to handing over prisoners while working to improve the system.

Colvin, who was based in Afghanistan in 2006 and 2007 with Canada's foreign service, previously told the committee that Mulroney tried to quash his repeated warnings about detainees being tortured.

"The view that I muzzled him or any other official is wrong," Mulroney, now Canada's ambassador in China, told the committee.

Mulroney acknowledged there was no way to get credible evidence about abuse of Canadian transferees because there was no proper monitoring of prisoners prior to 2007.

Mistreatment allegations 'known to us'

An Afghan police officer stands guard in a prison in Laghman province, east of Kabul. (Rahmat Gul/Associated Press)

"The fact that there were allegations of mistreatment in Afghan prisons was known to us," Mulroney said. "There was no doubt in anyone's mind that the Afghan system was riddled with problems."

However, Mulroney said there was no evidence that detainees being handed over by Canadian soldiers to Afghan officials were being tortured.

"He never brought forward any, and I think Richard would say this, any report alleging mistreatment of a Canadian-transferred detainee," Mulroney said.

Colvin testified that his warnings about torture were at first mostly ignored, but by April 2007 he and other Foreign Affairs staff were receiving written messages from government officials not to discuss issues via email or on paper in the future, but instead use the telephone.

But Mulroney told the committee that ideas, opinions and strongly held views were "often best first expressed by phone, first expressed."

Mulroney said one can't do work of that nature — with officials on three continents and divided by several time zones — exclusively through email exchanges.

Mulroney also praised the former diplomat for his "bravery and dedication" to volunteer in a dangerous theatre of operations.

He said Colvin was one of a large number of people who brought ideas, suggestions and recommendations, adding that he didn’t always agree with him but listened to what he had to say.

Bloc Québécois MP Claude Bachand presented Mulroney with a document obtained by CBC News where Colvin wrote about Afghan prisoners complaining of being whipped, shocked and cut.

Mulroney said he remembered receiving Colvin's report but that those prisoners weren't, to his knowledge, people captured by Canadians.

But Mulroney, when asked, could not say definitively that the detainees had not been transferred by Canadians.

The government and the opposition had both been eager to have Mulroney testify. The opposition parties also have been calling on the government to release a series of uncensored documents they say they need in order to do a thorough job questioning Mulroney.

With files from The Canadian Press