BARCLAYS could be forced to update its data protection and customer security systems after an information breach saw the details of thousands of customers put up for sale.
The bank is analysing the details of customers to find out who was affected and how their details were stolen from Barclays Financial Planning Services, a unit that was closed in 2011.
Those analysed so far all come from 2008, which the bank hopes means the information, such as passport numbers, salaries and healthcare data, is now out of date.
The details of at least 2,000 customers were given to the Mail on Sunday by a broker who claimed another 27,000 were also for sale.
"We will take all necessary steps to contact and advise those customers as soon as possible so that they can also ensure the safety of their personal data," said the bank in a statement.
"Protecting our customers' data is a top priority and we take this issue extremely seriously. This appears to be criminal action and we will co-operate with the authorities on pursuing the perpetrator."
The Financial Conduct Authority is investigating the bank over the breach.
"Barclays have contacted us and we will be working with them to understand exactly what has happened and what steps consumers may need to take," said an FCA spokesperson.
"Consumers rightly presume their data is safe with their bank, and this should serve to remind all firms how important it is they have the correct procedures in place to ensure data is secure and used appropriately."
Although the cause of the breach has not yet been identified, it is understood one possible outcome is a fine for the bank.
Another likely result would see Barclays forced to upgrade its data security systems, though the bank is understood to have done so since 2011, when the unit was shut down.
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