The error occurred in tax credit renewal forms that are sent to claimants to ensure that HM Revenue and Customs has correct details for information such as salary, current living arrangements and banking details.

The printing problem resulted in some pages of the documents being out of order, and some recipients receiving details of another claimant.

A spokesman at HMRC said that the issue was a "print-run error" rather than a data issue. "We don't want our customers to panic. Their details are not at risk," he said, adding that from the information available within the forms there is no danger of bank accounts being accessed or ID fraud.

"We've been assured by our data security experts that this is not possible," he said.

HMRC would not reveal the identity of the printer concerned, but said that the incident would prompt some form of investigation.

In a statement HMRC said that it "takes data security extremely seriously. Unfortunately an error has occurred in one of the tax credits print runs causing some customer information to be wrongly formatted.

"Investigations are underway to identify the cause of the problem and we will be contacting affected customers in writing this week, apologising and providing a corrected award notice. An initial analysis shows that ID theft could not result from this printing error."