According to Australian press reports, statements including the account names, numbers and balances of 397 customers were posted to the wrong people after a computer crashed in the bank's post department.

NAB was alerted to the breach last week when a customer told the bank that she had been sent another person's account details.

Around 418 NAB customers who received wrong statements — some received more than one — were asked to destroy them.

NAB spokesman Geoff Lynch told reporters that the bank took full responsibility for the incident. Affected customers were informed of the blunder by phone and were sent a formal letter of apology.

Lynch claims there is nothing in the statements that exposes anyone to fraud risk.

The bank says it has informed the Federal Privacy Commissioner, the Banking and Financial Services Ombudsman and the Australian Prudential Regulatory Authority of the incident.

Last month UK high street bank Hbos said it had launched an investigation into how a customer who requested a copy of her bank statement ended up being sent the confidential details of 75,000 other account holders.