An inmate holds a child in the background as she walks in the yard at a prison in Kabul, Afghanistan. Former diplomat Richard Colvin says captives were turned over to Afghan prison officials by the Canadian military in 2006-07, despite his warnings that the detainees would be tortured. (David Guttenfelder/Associated Press)

Certain information related to the Afghan detainee controversy has to be kept secret to protect lives, International Trade Minister Stockwell Day said Friday in defence of his government's decision not to release critical documents.

Day said government officials routinely make decisions on what information needs to kept classified. It would be "naive" to release info about high-security missions, including details on battlefield captures or the discovery of militants' hideouts, he said.

"There are details of which, if they were to be publicly made available, would only help the enemy. So the law is very clear that there are situations where there could be security issues where certain elements of an operation must be protected."

Trade Minister Stockwell Day says certain information related to the Afghan detainee affair has to be kept secret to protect lives. (Adrian Wyld/Canadian Press)

Day's comments come a day after the Liberals, NDP and Bloc Québécois passed a motion in the House of Commons demanding the release of thousands of documents in uncensored form, including reports written by Richard Colvin.

Colvin, a former senior diplomat with Canada's mission in Afghanistan who's now based in Washington, says captives were turned over to Afghan prison officials by the Canadian military in 2006-07, despite his warnings to the Canadian government that they would be tortured.

Reporters questioned Day as to how Colvin's diplomatic reports could include military mission-related details.

Day repeated that any elements that could affect the security of Canadian soldiers or civilians would be protected.

The government has repeatedly said it is legally barred, by terms of the Canada Evidence Act, from releasing sensitive information about the Afghan mission. In a letter made public Tuesday, parliamentary law clerk Robert Walsh, Parliament's expert on the laws that affect it, dismissed that reason as "absurd."

Day said if opposition members looking at redacted documents want the censored details, there is a process for them to appeal.

Meanwhile, Peter Tinsley, the departing chair of the Military Police Complaints Commission has taken the Harper government to task for refusing to renew his term in the middle of the Afghan detainee controversy.

It is unprecedented for the government not to renew his appointment as head of the military oversight body, Tinsley said. His last day on the job was Friday.

His departure will effectively halt the commission's ability to continue the public hearings — and send a "chill" through other quasi-judicial bodies whose heads are appointed by the government.

With files from The Canadian Press