A public hearing into what the Canadian army may have known about the alleged torture of Taliban prisoners in Kandahar has been postponed amid accusations of government obstruction.

The Military Police Complaints Commission has been overwhelmed with motions filed by federal government lawyers and has decided to delay the opening of the inquiry, slated for Monday, until Wednesday.

The delay came as the Conservative government faced more accusations that it's trying to obstruct the investigation into allegations that Canada allowed the transfer of prisoners to Afghan jails, even though torture was considered commonplace.

Defence Minister Peter MacKay denied Thursday in the House of Commons that federal lawyers are trying to block the testimony of a key witness, diplomat Richard Colvin.

As former political director of the Kandahar provincial reconstruction base, Colvin — through his lawyer — has said he has information relevant to the commission's investigation. But federal lawyers have tried to get him stricken from the list of witnesses.

MacKay suggested the diplomat would have nothing to add to the investigation. But a letter, obtained by The Canadian Press, shows the Defence and Justice departments have no idea what evidence Colvin might possess.

The letter, written Sept. 30 and signed by lead Crown lawyer Alain Prefontaine, said the diplomat's claims that he has knowledge of what military police knew about the alleged torture of prisoners "require clarification."

Specifically federal lawyers said they want to know with which military police officer Colvin "shared information concerning the risk of torture of detainees at the hands of Afghan authorities; when this information was shared; and whether this information was shared orally or in writing."

There have been accusations some prisoners, captured by Canadians but handed over to Afghanistan's notorious intelligence service, were abused. Two human-rights groups, Amnesty International and the B.C. Civil Liberties Association, claim that Canadian authorities either knew about the alleged torture or should have known.

A Federal Court decision recently narrowed the inquiry's scope to the conduct of military police officers.

MacKay denies 'political interference'

And it's on that basis that MacKay told the House of Commons that the government wanted Colvin removed from the witness list, along with 22 other senior federal officials and military officers.

MacKay denied the government was trying to hide anything.

"This is not politically motivated," he said responding to questions from NDP Leader Jack Layton. "There is no political interference."

He said the investigation is being conducted by the commission, which is an arm's length agency set up to investigate complaints against military police.

But Layton wasn't buying it and said it's "pretty clear they don't want to hear from Mr. Colvin."

MacKay said the government is prepared to provide dozens of other witnesses and has handed over hundreds of documents that deal specifically with what military police officers knew and didn't know about possible torture.