The Law Council of Australia has called on the federal government to drop its endorsement of David Hicks' military trial after a damning new report by top silk Lex Lasry, QC.

Law Council president John North said Hicks' chances of a fair trial had deteriorated even further as new concerns were raised about the fairness of the military commission process.

"The Law Council has therefore urged the Australian government to put pressure on the United States government immediately to bring Mr Hicks before a properly-constituted trial, not a military commission," he told reporters in Melbourne.

"If that cannot be done then we have asked that he be immediately released back to Australia.

"We are saying that it is impossible for Mr Hicks to get a fair trial where the US Department of Defence plays the accuser, jailer, prosecutor, defence attorney, judge and jury in a matter."

Mr Lasry's latest report found there was a "significant risk" the trial would adopt witness statements from fellow detainees, which may have been given under duress, without testing them.

Some of those detainees had been released and were unlikely to be returned for cross-examination, Mr Lasry said.

"Any statement that's made by a witness or an accused which is the product of physical coercion is obviously tainted, primarily because it's not voluntary," he said.

That concern was added to a litany of existing criticisms of the military commission including its lack of independence, the commission members' lack of legal training, the absence of rules of evidence and the lack of an appeal process.

Mr Lasry has been appointed by the Law Council of Australia to observe legal proceedings against Hicks.

He criticised Prime Minister John Howard and Attorney-General Phillip Ruddock for refusing to acknowledge flaws in the legal process.

"The prime minister has, as recently as a couple of days ago when he was in Washington as I recall, expressed the view that he thought the process was fair," Mr Lasry said.

"It is, with great respect to the prime minister, incomprehensible that anyone could look at these rules and see how this process works and think it was fair, particularly dealing with a person who's now been in custody for a period of four years."

Mr Lasry said Australia's "moral authority" was at risk by condoning the trial.

In reply to a draft of Mr Lasry's report, Mr Ruddock told the Law Council there was no evidence Hicks had been mistreated nor that the commission members were not independent.

Nevertheless, the federal government had sought assurances from the US there was enough evidence to proceed against Hicks after noting claims by his lawyer "that the prosecution case is based largely on hearsay evidence", Mr Ruddock wrote.

A US court last week cleared the way for Hicks to be tried on charges of attempted murder, conspiracy to commit war crimes and aiding the enemy.

Hicks, 29, has pleaded not guilty to the charges.

He has been detained at Guantanamo Bay since January 2002, following his capture among Taliban forces in Afghanistan in late 2001.