New Zealand's Commerce Commission has called for more farmers to come forward to detail their experiences with interest rate swaps as part of a probe into allegations banks mis-sold the complex instruments to small farm businesses.Complainants to the Commission estimate ANZ, Westpac and other unnamed banks may have sold as much as NZ$4 billion worth of these products to farmers between 2005 and 2009. They allege they didn't understand the complexity of the products or that they would not benefit from falling interest rates. Banks in the UK may have to pay out £1.5 billion to small businesses that were mis-sold similar swaps products. The Commission began its investigation in August, following a campaign by the Sunday Star Times newspaper, and has already spent 1000 staff hours on the investigation, which it said was still at an early stage."We have information from around 60 complainants at this stage, but will need more people to come forward if we are to form a complete picture of the issue," said Commission chairman Mark Berry. "We are not only interested in people who feel that they have been misled, but also those who are satisfied with the way the product was sold to them," he said.Farmers' lobby group Federated Farmers has welcomed the Commission's call for more farmers to come forward. It said it would help promote the investigation to farmers."If farmers have concerns about the mis-selling of swaps then now is the time to raise them with the Commerce Commission," said Bruce Wills, Federated Farmers' president, who is also a former banker.The Commission has set up a special website which has details about the investigation, a question and answer section, and a questionnaire for farmers. Elsewhere, Opposition Labour MP Damian O'Connor has said a full parliamentary inquiry should be launched if the Commission's inquiry stalls.