The personal details of 600,000 people interested in joining Britain's armed forces have been lost after a laptop belonging to a Royal Navy officer was stolen, the Ministry of Defence disclosed tonight.
It is the latest extraordinary data loss incident involving a Government department and potentially the most serious as recruits to the armed forces are targets for terrorists.
The laptop containing the data was stolen from a vehicle parked overnight in the Edgbaston area of Birmingham on Jan 9 but was only made public late tonight.
Des Browne, the Defence Secretary, is expected to appear before MPs next week to explain the latest Government data crisis which follows the loss of 25 million child benefit records and 3 million learner driver details in the last few months.
The MoD disclosed that the laptop contained information on 600,000 people who have expressed an interest in joining the Royal Navy, Royal Marines and Royal Air Force.
For those who submitted an application to the forces "extensive personal data" - including passport details, National Insurance numbers, family details and medical records - has been lost.
The laptop also contained the bank records of at least 3,500 people.
"The Ministry of Defence can confirm that a laptop was stolen from a Royal Navy officer in Birmingham last week, on the night 9/10 January, and as a result, a large quantity of personal data has been lost," the MoD said in a statement on its website.
"After consultation with West Midlands Police about the impact on the investigation, were the theft to become public knowledge, we did not immediately make public the loss of this data. We have, however, decided that it would now be right to do so.
"The Ministry of Defence is treating the loss of this data with the utmost seriousness. We are writing to some 3,500 people whose bank details were included on the database.
"Action has already been taken with the assistance of APACS [Association for Payment Clearing Services] to inform the relevant banks so that the relevant accounts can be flagged for scrutiny against unauthorised access."
The Government also admitted tonight that hundreds of highly personal state benefit documents had been found scattered near a roundabout in Exeter, Devon.
The papers included details of people's home loans and mortgage interest, details of National Insurance numbers, addresses and dates of birth. It is the second time in the past few months that such information has been dumped at the same location.
Opposition parties have rounded on the Government over its latest data blunders.
Chris Grayling, a shadow Cabinet minister said: "This is just utter incompetence from the Government.
"You would have thought that after the child benefits fiasco they would have treble checked the security of all personal data in all Government departments.
"Ministers have clearly been both irresponsible and negligent. It's just not good enough."
People who are concerned that their data may have been on the laptop are advised to email recruitdata@check.mod.uk from Saturday at 10 am onwards.
The MoD also plans to establish a helpline.