Wheat exporter AWB believes new allegations of kickback-style payments are designed to hurt the company's monopoly power to export wheat, according to the Australian Broadcasting Corporation.

Former employees of AWB allege bribes were paid to officials in Pakistan, Indonesia and Yemen during the 1990s, the corporation said.

A judicial inquiry will begin next month into earlier allegations that AWB paid bribes to Saddam Hussein's regime in Iraq.

The company's Peter McBride says while there is concern about the new claims, they are yet to be substantiated.

"One of our main concerns is that we are continually attacked by unnamed sources," he said. "Currently AWB has a culture based around performance to obtain the best price possible for the Australian wheat growers, but we always act ethically and properly in our export duties."

The federal opposition is demanding the government broaden the inquiry into AWB and the Iraqi oil-for-food scandal. Labor's Kevin Rudd says the prime minister has admitted government officials travelled with AWB to Iraq and he wants to know what reports came back.

"That's why they've tried to construct a commission of inquiry which points the finger at the wheat board and lets the government off scot free," Rudd said.

Trade minister Mark Vaile has side-stepped questions over when the government first became aware of AWB's commercial arrangements. "We should leave it to that commission of inquiry to seek out the information and the evidence," Vaile said.