A few years after the bruising royal commission into financial services, poor behaviour is creeping back into the banking sector, as evidenced by the shortchanging of hundreds of thousands of customers with mortgage offset accounts.

ASIC chairwoman Sarah Court is reading banks the riot act after a report detailed a litany of problems in the $350 billion mortgage offset account market.

The corporate regulator found Australian banks paid more than $55 million in compensation in just two years, for failures with mortgage offset accounts, warning customers could be…