Oxfam claims it has evidence the big four Australian banks are financing companies involved in land grabbing, child labour and illegal logging.
The ABC says a report for the organisation, Banking on Shaky Ground, identifies four cases in Cambodia, Papua New Guinea, Indonesia and Brazil where the banks funded companies accused of improperly or illegally acquiring land from the people.
Oxfam chief executive Helen Szoke said National Australia Bank, Commonwealth, Westpac and ANZ were not living up to their image as global leaders in sustainable banking.
"There is a gap between what the big four banks say they do and what they actually do," she said.
"We think there is a real problem around due diligence - around them actually focusing on their investment practices and making sure they put their money where their mouth is, in terms of ethical and sustainable investment practices in these agricultural businesses overseas."
According to Dr Szoke, Oxfam's research shows that the banks' exposure to companies in the agricultural commodities industry is in excess of $20 billion.