The Public and Commercial Services Union (PCS), one of the UK’s largest trade unions, is blaming the loss of millions of child benefit records on the “enormous pressure” placed on HM Revenue and Customs (HMRC), imposed by job cuts.

It was revealed last night that the personal details of 25 million Britons, including names, addresses, birth dates, national insurance numbers and bank account details, of every child benefit claimant in the country has gone missing.

The confidential material, saved on two CDs that were not encrypted, was put in the post by a junior worker at HMRC. The mistake has triggered serious concerns over ID fraud risks.

Mark Serwotka, general secretary of PCS, said: “The extremely serious loss of confidential data should be set in the context of the enormous pressure being placed on HMRC by government imposed job cuts totalling 25,000 by 2011, the recent merger and massive ongoing restructuring, which will see large scale office closures. With additional security checks expected to be put in place for people claiming and making enquiries about child benefit, we urge the government to put extra resources into HMRC rather than continuing with cutting jobs.”

He added: “The union and its members are co-operating with the department and the authorities in their enquiries into the missing child benefit data.”

Paul Gray, the chairman of HMRC, has resigned over the incident. Jonathan Baume, general secretary of the FDA, the union for senior public servants, said of his departure:

“There has been a serious operational error, which should not have occurred. Paul Gray was in no way personally responsible, but he has recognised that, as the most senior official in the department, the accountability ultimately lies with him. His decision to take on this accountability is an example of British public service at its best.”