SWINDON-BASED building society Nationwide is at the centre of a security lapse that may have put 11m 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, which has its headquarters in Pipers Way, is writing to all of its 11m customers about the importance of security.

A Nationwide spokesman said the laptop was security protected, but would not give details. He also reassured customers they are not at risk of fraud.

"The information is not on its own enough to allow you to commit identity theft," he explained. "We can confirm there has been no loss of money from customer accounts as a result of this incident."

Nationwide apologised to customers and confirmed it has since tightened up security procedures.