Financial watchdog scrutinising banks over concerns mortgage holders are being ripped off

Australia's financial watchdog is probing whether bank customers are being ripped off because savings from mortgage offset accounts aren't being properly passed on.

Of the more than 3 million Australian households that have a mortgage, more than half feature an offset account.

Used correctly, they can save borrowers thousands of dollars a year by ensuring extra savings offset the outstanding balance on a home loan, leading to less of an interest bill.

READ MORE: Officers killed in Porepunkah shooting named

There is some $300 billion sitting in offset accounts across Australia.

However, 9News can reveal the Australian Securities and Investments Commission (ASIC) is concerned customers might not be getting those proper savings due to bank errors.

"We've heard, in some instances, the banks have not connected the offset account to someone's mortgage account," commissioner Kate O'Rourke said.

"That's bad for the consumer, but we're not sure how widespread that problem is.

READ MORE: 'This will unsettle the RBA': Shock inflation result revealed

ASIC has now launched a surveillance program of eight banks, including some of the big four, and has hinted refunds could be on the cards if it finds customers have been missing out on their deserved savings.

"Our expectation is that when things have not been properly done, consumers are remediated," O'Rourke said.

The program could take a year to find out how many people have been impacted.

In the meantime, consumers have been advised to carefully check statements and ask their bank to confirm accounts are linked if they are in any doubt.

DOWNLOAD THE 9NEWS APP: Stay across all the latest in breaking news, sport, politics and the weather via our news app and get notifications sent straight to your smartphone. Available on the Apple App Store and Google Play.