TORONTO - A terrorist collaborator is walking the streets because a Canadian judge wrongly decided to stay extradition proceedings against him, the federal government asserts.

In documents filed with Ontario's highest court ahead of an appeal hearing, Ottawa maintains Abdullah Khadr should be handed over to the United States to face terror-related charges.

Instead, by ordering the stay, Ontario Supreme Court Justice Christopher Speyer put Canada's security at risk and damaged the fight against terrorism, the government argues on behalf of the U.S.

"Because of the extradition judge's errors, an admitted al-Qaida collaborator walks free," the documents state. "The security of Canada and the international community is put at risk, Canada's fight against terrorism is undermined, and the interests of justice are not served."

The U.S. wants to try the Ottawa-born Khadr, whose younger brother Omar is serving time in Guantanamo Bay for war crimes, on charges of supplying weapons to al-Qaida in Pakistan.

Khadr's lawyers argued for the stay on the grounds his self-incriminating statements were the product of torture in Pakistan in which the Americans had been complicit.

In their factum filed last week, they argue Washington's appeal submissions have no legal merit, and play on fears of terrorism.

"These proceedings would not exist but for the U.S.A.'s misconduct," they say. "Justice Speyer found that allowing the matter before him to proceed would tarnish the integrity of his court."

The American case against the Canadian citizen, who turns 30 next month, is based on three self-incriminating statements Khadr gave: two to the FBI and one to the RCMP.

Speyer decided the FBI statements were tainted as the result of Khadr's abuse during 14 months in Pakistani detention, and therefore inadmissible.

However, the judge said Khadr's confession to the RCMP -- made in December 2005 on his return to Canada -- was admissible, and sufficient to order his extradition.

The judge nevertheless stayed the proceedings last August on the grounds that American conduct in Khadr's arrest and detention in Pakistan had been egregious.

The judge noted the U.S. had put up a $500,000 bounty on Khadr's head, interfered with his access to Canadian consular officials, and delayed his return to Canada by six months.

Speyer said the Americans had contravened "fundamental notions of justice," and extraditing Khadr would reward their behaviour.

While Speyer rejected Khadr's claims of sexual and physical abuse, he did find Pakistani agents mistreated the captive and deprived him of sleep.

"The sum of the human-rights violations suffered by Khadr is both shocking and unjustifiable," Speyer ruled.

Khadr's lawyers argue that Speyer was well within his rights to stay the extradition in light of the U.S.'s "gross misconduct."

But the federal government insists Speyer made numerous errors -- among them exceeding his authority, misapplying the law -- and could simply have excluded evidence he considered tainted.

It wants the Ontario Court of Appeal, which is slated to hear oral arguments next month, to send the case back to Speyer to assess whether there are grounds to extradite Khadr.

Khadr, who was freed from four years in custody in Toronto after Speyer's ruling, said at the time he just wanted a fresh start.

He is the oldest son of the late Ahmad Said Khadr, who was closely associated with Osama bin Laden and is alleged to have raised money for al-Qaida.