Federated Farmers is unhappy that the interest rates businesses are paying remain stubbornly high at the same time as home loan rates continue to tumble.
Official figures show floating mortgage rates are down a third since July while business lending rates have barely moved.
Federated Farmers says businesses, including farms, are picking up the tab for cheaper home loans.
It says Business New Zealand should be putting pressure on banks to reveal how interest rates are calculated.
But the business lobby group says a recent survey shows firms are more worried about credit availability than high interest rates.
It says Federated Farmers needs to accept that banks are in the best position to assess the risks associated with different borrowers.