The reduced net profit after tax guidance compounds what was already expected to be a half-year profit result that was 50 per cent lower than the previous corresponding period when the company posted a $22.3m profit.

AWB says a management review of its Brazilian operations identified the accounting errors which reduce net profit after tax for the year ending 30 September 2008 by $4 million.

The 30 September 2008 comparatives will be restated, and AWB says management changes have been made in AWB Brazil.

"Due to the poor first half performance of AWB Brazil and the current challenging business environment in Brazil, we are undertaking a comprehensive review of this business," AWB Ltd managing director Gordon Davis said.

"AWB's general manager commodities Mitch Morison will be based in Brazil to complete the management review of the business.

"Conditions in Brazil remain challenging and it is likely that we will emerge with a smaller and refocused business."

The errors were in the accounting treatment of certain contracts, particularly in the mark-to-market value of inventory.

Mr Davis said operating conditions in Australia during the first half have been solid in WA, Queensland and northern New South Wales but the ongoing drought has adversely affected trading conditions in Victoria, South Australia and southern New South Wales.

"As previously advised, Landmark Rural Services and its investments, particularly Hifert, have been adversely affected by these seasonal conditions," he said.

"Landmark Financial Services recorded a solid first half result due to active margin management on the loan book and a good contribution from insurance."

AWB will present its half year result on Wednesday, May 20.