New Zealand banks are yet to pass the full cuts from a drop in the official cash rate on to customers. 

Banks are again under fire in Australia, where the government has ordered an inquiry into why they're not passing on interest rate cuts to customers.

The Reserve Bank of Australia has cut the OCR three times since January, but Treasurer Josh Frydenberg says the big four banks have failed to pass those cuts on in full.

Mortgage broker Sue Tierney told Heather du Plessis-Allan that we're not seeing the full cuts from the floating interest rates being passed on to customers.

"Floating rates have only come down 0.6 per cent, but in actual fact, the OCR has dropped 0.75, three quarters of a percent in the last 18 months."

She says that banks have dropped their fixed percent rates, with many down by 0.84 per cent, but that clients tend to leave their rates floating.

"It's just so easy for the banks to make their margin that way."

However, Tierney says that she does not think government intervention is needed here as the banks here are paying attention to what is happening in Australia.