Amnesty International says Canada must join those calling for Omar Khadr's release from Guantanamo Bay, Cuba and his return to Canada.

Khadr stands accused of throwing the grenade that killed a U.S. soldier and injured another in 2002, when he was 15. He has been held in Guantanamo ever since.

"His rights as a child, including to be considered a child soldier were ignored. His right to freely choose his legal counsel -- ignored. His right to a fair legal process -- ignored. His right to be protected from torture and ill treatment -- ignored. Canada can no longer remain silent," said Alex Neve, secretary general of Amnesty's Canadian arm, during a Thursday news conference.

Neve was presenting an open letter to Prime Minister Stephen Harper that was signed by 25 current and former parliamentarians, including several former foreign affairs ministers, as well as academics, lawyers and human rights groups.

"This letter makes it absolutely clear that Canadians want the Canadian government to act now, to restore Omar Khadr's fundamental rights and to call for an end to the travesty of justice that Guantanamo Bay has become," Neve said.

Speaking on CTV's Mike Duffy Live, NDP defence critic Dawn Black said she supported Amnesty International, citing previous precedents from other governments.

"The British, the Australians, other countries have insisted that their nationals be taken out of Guantanamo, and brought back to their country of origin to face prosecution. And that's what should happen in this case," she said.

But Liberal foreign affairs critic Ujjal Dosanjh said the main concern should be fair justice for Khadr, rather than bringing him back to Canada.

"The issue is not where he's tried, the issue is natural justice and due process. I agree with (U.S. former secretary of state) Colin Powell. He said Guantanamo Bay should be shut down, and all of the prisoners should be streamlined into the American justice system, and let them be tried before appropriate and regular courts," he said.

A U.S. military judge dismissed the charges against Khadr last week on a technicality, but the U.S. has not moved to release him and has asked the judge to reconsider the decision.

Omar Khadr is the son of Ahmed Said Khadr, an Egyptian-born alleged al Qaeda financier who was killed in 2003 in Pakistan when a military helicopter attacked the house where he was staying with some senior al Qaeda operatives.

Omar and some of his brothers are believed to have fought for al Qaeda and stayed with Osama bin Laden.

One of Khadr's brothers, Abdullah Khadr, has been accused of supplying weapons to al Qaeda and is currently being held in Canada on a U.S. extradition warrant.

On Wednesday, Minister of Foreign Affairs Peter MacKay said the government will not request Khadr's release until the appeals process has been exhausted.

But Neve and others maintain Khadr should be dealt with under Canadian law.

"His case now almost stands alone in terms of individuals who have been abandoned by their government," Neve said.

"Governments throughout Europe, the Australian government, of course, recently with the case of David Hicks, have all intervened forcefully and generally successfully with the U.S. government on behalf of their nationals."

Neve also accused Ottawa of being hesitant to intervene because politicians are worried about U.S. criticism that Canada is a haven for terrorism.