The Westpac bank in Australia has come under fire after deciding to charge customers interest on their interest, and flagging further rate rises.
Westpac Australia is the parent company of Westpac New Zealand.
The ABC reports the bank has announced that customers will be charged interest on credit card fees and interest charges starting from June.
It has defended the move, saying it will not apply to customers who pay off their credit cards.
Christopher Zinn from from consumer watchdog Choice says the bank is aware many people will not be able to do that.
But Australian Bankers Association chief executive Steven Munchenberg says Westpac is not acting unfairly.
"When you save money in a bank, you actually earn interest on interest, so this is in many ways the other side of the equation," he says.
"All Westpac is doing is just saying that they will charge you interest on the amount of money you owe the bank."