The UK's tax authority shut down a tax-credits website last week, and a criminal investigation is underway concerning possible identity theft, a spokesman confirmed today.

HMRC (HM Revenue and Customs) identified and stopped attempts at fraud during compliance checks on its tax credits e-portal, the agency said in a news release. New checks are being developed to ensure the system is secure, it added. No other systems were affected.

The fraud involved internal information concerning workers at the DWP, or Department for Work and Pensions, the spokesman said. The criminal investigation revolves around the apparent false use of a number of DWP identities in fraudulent tax credit claims. No external DWP records were affected, according to the agency.

A hotline has been set up for those who believe they may have been affected. Since a criminal investigation into the case is ongoing, further details could not be released, the spokesman said.

DWP provides state financial support to 11 million pensioners and helps people plan for retirement.