Defence Secretary Des Browne is set to make a statement to MPs on the theft of military laptop containing the personal details of 600,000 people.
Defence Secretary Des Browne says a probe into the loss of a laptop with details of 600,000 people has uncovered two similar thefts since 2005.
Information Commissioner Richard Thomas said it was "a very disturbing incident" and asked why such sensitive data was allowed out of the office.
The theft from a car in Edgbaston which sparked the internal inquiry came after a Royal Navy recruiting officer failed to follow security procedures, he said.
The data includes passport and National Insurance numbers and bank details.
The other two laptops held similar data but on fewer people, he told MPs.
They relate to people who had expressed an interest in, or joined, the Royal Navy, Royal Marines and the RAF.
Mr Browne said it should "never happen again". Shadow defence secretary Liam Fox called it a "dreadful mess".
Mr Thomas said the Ministry of Defence laptop incident was "a stark illustration of the potency of personal information in a database world".
In his statement, the defence secretary announced a full investigation "into how these weaknesses came about" by Sir Edmund Burton, chairman of the Information Advisory Council.
Power of technology
Laptop recall
He said he hoped Mr Browne, due to address MPs after 1600 GMT, would announce a full investigation into the loss.
Mr Browne said data on the laptop stolen in Edgbaston on 9 January included passport, National Insurance and driver's licence numbers, family details and NHS numbers for about 153,000 people who applied to join the armed forces.
"It needs to have a wide remit," he told BBC Radio 4's Today programme.
Banking details were also included for around 3,700 people, he said.
"Why is so much information being collected and held in the first place?
Ministers were informed on 14 January that the information was not encrypted. The police were called and all similar laptops were recalled within the next four days.
"Why is it allowed out of the office on a laptop? We need to have a full review of other incidents involving laptops."
Mr Browne said the intelligence services had told him there was no indication that the unencrypted files had fallen into the hands of extremists, but it could not be ruled out.
He said government departments needed to carry out "privacy impact assessments" of the sensitivity of the data they are holding.
Careers office
"I don't think people across the public sector have fully woken up to the power of technology."
Action is being taken against the officer concerned and following an internal Royal Navy investigation "steps are being taken to prevent a reoccurrence" of the incident, he said.
The laptop was taken from a Royal Navy recruitment officer's car parked in Edgbaston, Birmingham, on 9 January.
He also disclosed that "two further laptops, potentially containing similar data" were stolen since 2005.
Family details
A Royal Navy laptop was stolen from a car in Manchester in October 2006 and an army recruiting laptop stolen from a careers office in Edinburgh in December 2005.
But the theft was only disclosed on Friday night by the MoD after details began to leak out.
The MoD said it was treating the theft with the "utmost seriousness".
Entries on the computer also included drivers' licence details, family details and doctors' addresses, the MoD said.
The missing laptop is a black COMPAQ Evo N600c with a 1.5in silver line running top to bottom, right of centre, and with the words COMPAQ in red ink.
It also has a fixed mouse area with a blue rubber cursor button between keys.
Child benefit records
The black left rubber foot on the underside of the laptop is possibly missing and one of the catches on the lid is possibly broken.
According to police, the laptop was stored in a black fabric case when it was taken, and it went missing along with a silver Nokia 6030 mobile phone.
Separately, hundreds of documents containing sensitive personal data have been found dumped on a roundabout in Devon.
Details of benefit claims, passport photocopies and mortgage payments were included in the confidential data found near Exeter Airport.
Last November, it emerged that 25m child benefit records had been lost after HM Revenue and Customs (HMRC) sent two unregistered and unencrypted discs to the National Audit Office.
