The UK's fourth largest building society apologised to customers today after their names, account numbers and balances were accidentally revealed to other members.
Skipton Building Society said a third party printing error led to the details of 3,115 customers with passbook accounts being printed on the back of other people's statements in a recent mailing.
But it stressed that the details revealed were not enough to put customers at risk of fraud, as the accounts required a signature to make withdrawals and could not be used over the internet.
Despite this, it has written to all affected customers, apologising and offering them a new account number for additional peace of mind.
A Skipton spokesman said: "The details did not include the other customers' address, date of birth or other identifying details. The risk to affected customers is negligible because of this.
"Nevertheless, we have written to those affected to apologise and to reassure them that the correspondence contained insufficient information to enable any unauthorised transactions on their accounts.
"We are also offering to change the account numbers of any customers seeking additional peace of mind."
The incident affected 3,115 people out of a mailing list of 108,000 customers who were being sent an annual account summary.
Skipton said the City watchdog, the Financial Services Authority, had been made aware of the incident which happened at the end of January.
The group is the latest in a long line or financial services firms and Government departments to wrongly publish or lose customers' data.
In October last year insurance giant Zurich said it had lost a tape containing the personal details of 51,000 UK customers.
In November 2007 HM Revenue and Customs lost two computer discs containing the entire child benefit database.
The discs held personal information on 25 million people, including names, addresses, dates of birth and National Insurance numbers.
In October 2008, accountancy firm Deloitte had a laptop containing personal details of more than 100,000 members of the Network Rail and British Transport Police pension schemes stolen.Reuse content