A number of disgruntled current and former shareholders of AWB Ltd are suing the wheat exporter for $25 million over its role in the Iraqi oil-for-food scandal.

Law firm Maurice Blackburn Cashman said today that it would begin a shareholder class action against AWB in the Federal Court.

AWB said the proposed class action was "ill-conceived".

"If the proceedings are issued, they will be vigorously defended," AWB said.

The managing principal of the Maurice Blackburn Cashman's NSW branch, Ben Slade, said the firm was acting for an unspecified number of institutional and retail investors in AWB who were claiming they lost money because AWB failed to inform the stock market of its activities in Iraq.

"We've been instructed by a number of victims of AWB's wrongful conduct seeking compensation for the losses that they've suffered as a result of that wrongful conduct," Mr Slade said.

Mr Slade said it was alleged AWB had failed to continuously disclose to the marketplace material facts that could reasonably be expected to affect the company's share price.

He said it was claimed that AWB should have revealed it was involved in taking steps that caused Australia to be in breach of United Nations sanctions under the oil-for-food program and by one means or another was getting money from a UN account to make payments to Iraq in breach of the program.

"That is a material fact that the sharemarket should have been told, and had they been told the share price of AWB shares would have been lower than it was," Mr Slade said.

"There are certain groups that wouldn't have bought any AWB shares at all, and there are others who would have bought at a materially lower price."

Mr Slade said the claimants estimated direct losses at about $25 million and there was also the possibility of claims for opportunity loss.

Australia's single desk wheat exports system is set for overhaul after AWB was found to have paid $290 million in kickbacks to Iraq between 1999 and 2003 under the UN's corruption-ridden oil-for-food program.

The Cole inquiry into AWB's kickbacks, which reported in November 2006, recommended 11 former executives face further investigation for possible breaches of criminal and corporations law.