Prime Minister Stephen Harper's office stood firm Tuesday in the face of growing calls for Omar Khadr's repatriation from Guantanamo Bay following the release of 2003 interrogation videotapes showing the detainee weeping and begging for help.

Khadr, a Canadian citizen, was only 15 when he was captured in a bloody firefight with U.S. troops in Afghanistan in July 2002, accused of throwing a grenade that killed a U.S. medic. Now 21, Khadr is the only Western foreigner still being held at the U.S. military prison in Guantanamo Bay, Cuba, and is awaiting trial before a military commission, scheduled to begin in October.

"Mr. Khadr faces serious charges. There is a judicial process underway to determine Mr. Khadr's fate. This should continue," Kory Teneycke, the prime minister's director of communications, told CBC News on Tuesday morning.

Teneycke refused to comment on the specific content of the video.

The statement came hours after Khadr's defence lawyers released a 10-minute video excerpt of hours-long interrogations by Canadian intelligence agents filmed over several days at Guantanamo Bay in late February 2003.

Opposition parties and human rights groups were quick to ramp up pressure on the federal government, urging it to call on the U.S. to allow for the Toronto-born Khadr to return home to face justice.

The video excerpts, selected by Khadr's defence lawyers, show the then 16-year-old Khadr weeping as he is interviewed by agents from the Canadian Security Intelligence Service.

Judicial not political process: PM spokesman

He also lifts his shirt to show them the wounds he says he incurred during the battle with American troops in Afghanistan six months before.

He had travelled to Afghanistan with other members of his family after the attacks against the U.S. on Sept. 11, 2001, to take part in al-Qaeda activities after Afghanistan's Taliban government was pushed from power.

Teneycke said the Canadian government would not seek Khadr's return to Canada on humanitarian grounds, as human rights groups and opposition politicians have been demanding.

"We might also add in terms of background that the Government of Canada's position is consistent with the previous government's," the spokesman said. "This is a judicial process as opposed to a political one."

Earlier Tuesday, Liberal foreign affairs critic Bob Rae called for Khadr's return, saying the previous Liberal government's decision was in line with what was then known about the case.

Based on new revelations, Rae said, "I think the question is what do we do now?… And the answer is we bring him home."

Government's stance 'disgraceful': NDP

NDP human rights critic Wayne Marston called the government's stance on the case "disgraceful" and an example of why there should be legislative oversight of CSIS.

"The prime minister has an obligation to bring this young man home," Marston urged.

Khadr's defence lawyers have repeatedly called for their client to be repatriated, arguing he was a child soldier and was tortured to extract confessions. With Tuesday's release of the videotapes, they hope to spark public support for their efforts to see their client returned home.

"What these tapes show is not a dangerous terrorist but a frightened boy and so the justification for Omar's ongoing detention and treatment as an adult in Guantanamo Bay is really without foundation," Khadr's U.S. military lawyer, Lt.-Cmdr. William Kuebler, told CBC News from Washington.

"What we're asking for is a fair trial and that's not something that a Guantanamo Bay military commission provides," he said, adding that the Canadian government hides behind the unpopularity of the al-Qaeda-linked Khadr family.

In May, the Supreme Court of Canada ruled that the Canadian government had to hand over key evidence against Khadr to his legal team to allow a full defence of the charges against him, which include accusations by the U.S. that he spied for and provided material support to terrorists.

Last week, internal Foreign Affairs documents were released showing that Canadian officials knew Khadr had been sleep-deprived for weeks to make him more willing to talk during other interrogations.

The report says that Canadian official Jim Gould learned during a visit to Guantanamo on March 30, 2004, that Khadr had been put on a so-called "frequent flyer program," meaning he was not permitted to remain in any one location for more than three hours.