A missing British Ministry of Defence computer drive could contain details of as many as 1.7 million people who had shown interest in joining the armed forces.

The drive, reported missing a week ago by IT contractor EDS, was used with a recruitment system.

Armed Forces Minister Bob Ainsworth said yesterday that "in the worst case" the drive could hold details of 1.7million people. For casual inquirers this would be no more than their name and contact details. "But for those who applied to join the forces, more extensive personal data may be held," Mr Ainsworth said in a written statement to Parliament.

In some cases this would include data such as bank details, passport, National Insurance and National Health Service numbers, driver’s licence information and details of next of kin.

Mr Ainsworth said EDS believed it unlikely the data was encrypted, as the drive had been held in a secure area at its premises in Hook, Hampshire.

He said banks had been informed so they could monitor accounts for unauthorised access.

The MoD had also set up a helpline for those afraid they may be affected. The loss came to light after EDS conducted an audit of its data-handling procedures to comply with new government guidelines brought in after details of 25 million child benefit claimants were lost by the Revenue and Customs Department.

The Liberal Democrats said the latest loss was a scandal.

Last month, the MoD said two computer drives containing Royal Air Force personnel data had been stolen from a secure facility in Gloucestershire.

In July, the government said 747 laptops had been stolen or lost from the MoD in the last four years and only 32 had been recovered.