The Canadian government was today under fire for refusing to seek the repatriation of a teenage national held at Guantánamo Bay, who was shown desperately pleading for his country's help in recently released footage.

Liberal politicians and human rights groups criticised Canada's conservative prime minister, Stephen Harper, for the lack of action saying it undermined attempts to eradicate the use of child soldiers.

Toronto-born Omar Khadr's US military lawyer called on Harper to "stand up and act like a prime minister of Canada" and demand the teenager's return.

Footage of Khadr's Guantánamo interrogation was released this week by his lawyers, in the hope it would spur the government into bringing him into the Canadian justice system.

However, a spokesman for Harper said scenes of Khadr sobbing for his mother as he was interrogated by Canadian officials in 2003, would not sway the government's position.

"These videos were in possession of the previous government when they decided to pursue the judicial process for Mr Khadr to have his day in court in Guantánamo," Harper's chief spokesman, Kory Teneycke, said.

"The information is not new. We can't ignore the serious charges Mr Khadr is facing. The proper forum for determining his guilt or innocence is a judicial process not a political process. We're not affected by what's on the cover of newspapers."

Khadr's military lawyer, Lieutenant Commander Bill Kuebler, along with his criticism of Harper, said yesterday that the military tribunals at Guantánamo "aren't designed to be fair" and designed "to produce convictions".

He said anyone who watched Khadr whimpering for his mother and still believed he had vowed to die fighting with a bunch of hardened al-Qaida terrorists is "crazy".

"The tape shows Omar Khadr not as a hardened terrorist but as a frightened boy."

"It just shows how unreliable anything that they extracted from this kid is would be at trial."

Khadr, who was shown in the video aged 16 and questioned after severe sleep deprivation, will have to remain at Guantánamo until he is prosecuted for war crimes in front of a special US military tribunal, later this year.

The liberal Canadian senator and ex-general Romeo Dallaire told Canada Television's (CTV) Newsnet programme that Khadr is a child solider and should be treated and given the same rehabilitation that Canada devotes to other child soldiers around the world.

"We're getting stabbed in the back," Dallaire told the cable channel. "We have worked for years to assist other nations in eradicating the use of children in conflict. But our own country doesn't even want to recognise that our own citizen (is a child soldier). No matter what his politics are, it's totally irrelevant.

"He's a child soldier that was abused and he's a child soldier that needs to be brought back into a formal process we signed up for."

Khadr, the son of an alleged al-Qaida financier, is accused of throwing a grenade that killed a US Special Forces soldier during a 2002 firefight in Afghanistan in which he was badly wounded.

He was captured when he was 15 and could face life in prison if convicted

Amnesty International has described him as the first person to face trial anywhere in the world for war crimes allegedly committed when he was a juvenile.

The seven hours of grainy footage, recorded over four days of questioning by Canadian intelligence agents in 2003, shows Khadr breaking down in tears.

He is seen pleading for medical help for chest and back wounds that he said had not healed six months after his capture. He also described the torture and abuse he suffered at the hand of US officials.

Khadr denied killing Army Sergteant 1st Class Christopher Speer, of Albuquerque, New Mexico, during the 2002 battle in Afghanistan.

The footage was the first to publicly show interrogations inside the US military prison complex.