A security lapse by Nationwide Building Society may have put 11 million customers at risk of identity theft.
The Financial Services Authority is investigating the incident after an employee's laptop was stolen, containing sensitive customer account information.
The computer was taken during a domestic burglary in August, but details are only now coming to light.
Nationwide confirmed the laptop held customer information, but insisted this did not include pin numbers, passwords or information about financial transactions.
The building society is writing to all of its 11 million customers about the importance of security.Reuse content