The confidential financial data of a million UK customers has been found on a computer that was sold on online auction site eBay for £35.88.
According to a report by the UK's Daily Mail, a former employee at digital archiving firm Graphic Data sold the computer on eBay without erasing the hard drive.
IT manager Andrew Chapman, 56, from Oxford, bought the computer and discovered a treasure trove of private financial information, including names, addresses, sort codes and account numbers, credit card numbers and security data such as mothers' maiden names.
Reports say confidential data belonging to customers of American Express, Royal Bank of Scotland (RBS) and NatWest was stored on the hard disk.
It is thought the PC contained historical information relating to credit card applications.
RBS and its subsidiary NatWest have told the BBC that their customers' details are involved.
In a statement, RBS says: "The IT equipment that appeared on eBay was not planned to be disposed by the company and investigations are still ongoing to find out how this equipment was removed from one of Graphic Data's secure locations."
RBS says the incident is "extremely regrettable" and it is "taking every possible step to retrieve the data and ensure this is an isolated incident".
An eBay spokesperson told the BBC that the company was looking into the incident and will work with Graphic Data to establish how the PC came to be available for sale on its site.
Last year the UK's Nationwide Building Society was fined £980,000 by the Financial Services Authority (FSA) after an investigation into the theft of a company laptop from an employee's home exposed failings in its information security.
Personal data of a million bank customers found on computer sold on eBay for £35 - The Daily Mail
Bank customer data 'sold on eBay' - BBC