The potential number of people affected by the the loss of a hard disk containing MoD details could be a high as 1.7 million, defence minister Bob Ainsworth told parliament on Monday.
In a written statement to MPs, Ainsworth said that up to 1.7 million people who had enquired about joining up could have had their details compromised.
"The hard drive had been used with the TAFMIS recruitment system and may, in the worst case, contain details relating to 1.7 million individuals who have enquired about joining the Armed Forces," wrote Ainsworth.
Sensitive information that could have been lost includes such as next of kin details, passport and National Insurance numbers, drivers' licence and bank details, and NHS number, said Ainsworth.
The loss of the removable disk by IT contractor EDS was reported last week.