According to press reports the bank has confirmed that the review could result in further automation or offshoring, but no decision has yet been made.

NAB hasn't stated how many domestic jobs are at risk but Australia's Finance Sector Union (FSU) says it has been made aware that 424 Melbourne jobs in lending, direct sales and customer services are being reviewed by BPO firm Genpact to determine the possibility of moving them offshore.

The FSU says the latest positions under review deal with a range of highly sensitive personal data, including credit and lending details, account numbers and personal information.

Says Paul Schroder, FSU national secretary: "Customers are most concerned about the security of their personal financial data. If NAB decide to send more jobs offshore then greater amounts of data will be accessed and processed outside NAB's control.

"We are calling on the NAB to weigh up the reputation risks associated with this pursuit of low cost labour offshore at the expense of loyal employees here in Australia."

The latest news comes on top of the 175 jobs that have already been cut and a further 70 that have been earmarked to leave Melbourne for India, says the FSU.

The union says it has also been made aware of further reviews in the NAB's wealth management and business banking areas that could see more jobs offshored.

Last year NAB offshored 81 back office jobs from its finance and accounting unit to India under an outsourcing agreement with Accenture.