HM Revenue and Customs apologised yesterday after it sent the confidential details of thousands of tax credit claimants to the wrong people.
Tax credit renewal packs were posted to claimants but some mistakenly included the earnings, bank sort code and the last four digits of bank accounts of other claimants, while some received packs with the pages listed in the wrong order.
Up to 50,000 people overall were affected by the errors blamed on a printing glitch.
HMRC said initial analysis showed there was little danger of ID theft because only a small amount of details were disclosed.
“HMRC takes data security extremely seriously,” a spokesman said in a statement.
“Unfortunately an error has occurred in one of the tax credits print runs causing some customer information to be wrongly formatted.”
It is not the first time HMRC has been hit by an administration error. In November 2008, details on 25 million child benefit claimants were lost by the tax department.