The Liberals and the NDP say the government's appointment of a retired justice to review the controversial Afghan detainee documents is not enough and are calling for a full public inquiry into the matter.
Liberal Leader Michael Ignatieff said during question period Monday the Conservative "government keeps holding back the truth," and only a public inquiry will solve the issue.
Harper responded that retired judge Frank Iacobucci "will have access to all documents and he will give us a public report."
NDP Leader Jack Layton also urged for a public inquiry.
Earlier, in an open letter to Harper, Ignatieff called Iacobucci's appointment an "overdue admission that action must be taken."
While the Liberal leader praised Iacobucci's reputation, he said the mandate and deadline assigned by the government is unclear.
"The problem lies not with Justice Iacobucci but with the job you have given him to carry out. We do not know what his mandate or deadline will be, and we do not know whether or how he will report to Parliament and the Canadian people," Ignatieff wrote.
"A public inquiry would give him the power to demand materials from the government, to call witnesses and to subpoena testimony. An inquiry could establish the facts and make recommendations for the future.
"Anything less will fail to provide Parliament and Canadians with the answers they are entitled to."
The Conservatives announced Iacobucci's appointment on Friday as Parliament was set to collide on the issue of whether MPs could see the classified documents relating to Afghan torture in full.
The NDP was quick to denounce the move as a stalling tactic to avoid the real issue: whether Parliament can force the release of the documents.
The House of Commons voted in December to release the documents regarding what the government knew about the risk of torture of detainees captured by Canadian soldiers when they were handed over to Afghan authorities in 2006 to 2007.
The opposition parties have argued they need and have the right to see the secret papers in full, but the government has said they are a matter of national security.
Liberal MP Derek Lee has threatened to bring forward a motion to hold the government in contempt of Parliament over the matter.
The NDP has set a March 19 deadline for the government to release the documents before it brings forth its own contempt motion.
Iacobucci, 72, served on the high court from 1991 to 2005. He headed an inquiry into the overseas torture of three Arab-Canadians, which filed its report in 2008.
