The Opposition's foreign affairs spokesman, Kevin Rudd, says the Prime Minister's appearance before the Cole Inquiry tomorrow is unlikely to lead to any sanctions against government ministers.
John Howard is to answer questions from the Commission about his knowledge of almost $300-million dollars in bribes paid by wheat exporter AWB to the former Iraqi government of Saddam Hussein.
Alexander Downer and Mark Vaile appeared before the inquiry earlier this week.
But Mr Rudd says the Inquiry only has the power to determine if the AWB has committed criminal offences or not.
"The key challenge for the Prime Minister, if he has nothing to hide, is to widen the terms of reference and the powers available to Commisioner Cole.
"Until he does that, this Commission of Inquiry has one hand tied behind its back.
"People were stunned yesterday as to why there were limited questions of ministers - the reason for that is because the powers available to Commissioner Cole are so limited."