Putting a tax on water is an ill-conceived idea which will damage the regional economies in parts of the South Island, Federated Farmers says.
It believes plans that the Labour and Green parties have to introduce irrigation charges will end up more like a regional farming tax, damaging Canterbury and Otago.
A report by the New Zealand Institute of Economic Research for Federated Farmers calculates a water tax of 1 cent per cubic metre of water used for irrigation and stock purposes means $39 million would have to be paid out by farmers.
Water and environment spokesperson Ian Mackenzie said it was simply not fair.
"Water tax and irrigation is highly likely to put up the price of fresh fruit and vegetables grown in New Zealand and that will hand the market over to more cost-competitive but poorer quality products coming in from overseas - whether it's California, Australia or Asia," he said.
"We're concerned there seems to be a principle within Labour and the Greens that farmers have an unlimited amount of money to be taxed. There seems to be a view that irrigation equals water pollution but the science says that's simply not true."