The National Australia Bank accidentally sent personal information of around 60,000 customers to the wrong email account, the bank revealed on Friday.
The details - including names, addresses, and banking information like BSB and account numbers - belonged to a group of people migrating to Australia who had set up new accounts with the bank, NAB said.
When emailing the migrant banking customers to confirm their new account, the bank also sent another email to an "incorrect" address. It did not specify the incorrect address.
The bank blamed "human error" for the bungle. It said it had written to affected customers, and was working with the OAIC and ASIC on the issue. No unusual activity had been identified on the accounts, NAB said.
Around 40 percent of the affected customers had either closed or not used their accounts this year, NAB said, and the remaining 19,000 accounts had a balance of less than $2.
"We do not consider that customers need to take any action with their account," NAB general manager of international branches Peter Coad said in a statement.
"We are sorry for this error and we will continue to work hard to improve and strengthen our processes."