Phnom Penh  - Lawyers for two defendants in an upcoming trial of former Khmer Rouge leaders have requested the tribunal's foreign investigating judge be dismissed after allegations of bias.

So Sovann, defence lawyer for former Khmer Rouge head of state Khieu Samphan, told the German Press Agency dpa that he would file a motion late Monday or early Tuesday asking the court to force judge Marcel Lemonde to resign.

One of Lemonde's former investigators alleged that his team was instructed by the judge to look for evidence of guilt rather than evidence of innocence in their probe of the former Khmer Rouge regime leaders.

Under the system operated by the tribunal, the investigating judges must work impartially since both the defence and the prosecution rely on their investigative work.

"I want him to resign and go back to rest in France," So Sovann said. "I love justice and I want to find justice for my client."

So Sovann said Lemonde's duty as investigating judge was to treat all evidence in the same way, whether it pointed to the guilt or innocence of his client.

"But he didn't do that," he claimed.

The motion followed a similar complaint filed Friday by the defence lawyer for another defendant, former foreign minister Ieng Sary.

Lemonde's former chief investigator filed an affidavit to police in Australia on Thursday, accusing the judge of instructing the team in August to "find more inculpatory evidence than exculpatory evidence."

A tribunal spokesman said Monday that Lemonde had no comment.

"He will provide all necessary information to the [court] at the appropriate time," the spokesman said.

Ieng Sary and Khieu Samphan are scheduled to face trial along with Nuon Chea, known as Brother Number Two, and Ieng Thirith, who was the former social affairs minister and is the wife of Ieng Sary. Their trial is Case 2 of the court's schedule. It is not expected to start before the end of 2010.

The Khmer Rouge tribunal, known as the Extraordinary Chambers in the Courts of Cambodia, a joint UN-Cambodian process, is wrapping up the hearing of Comrade Duch, the former head of the Khmer Rouge torture prison in Phnom Penh known as S-21.

Duch is on trial for crimes against humanity and grave breaches of the Geneva Convention. That trial will conclude next year. At least 15,000 people were said to have been tortured and executed at S-21 in the 1970s.

The Khmer Rouge ruled Cambodia between 1975-79. Up to 2 million people are thought to have died during that time from execution, starvation and overwork. The regime's leader, Pol Pot, died in 1998. (dpa)