Several government departments were involved in the loss of personal data
Sensitive data potentially affecting more than four million people was lost by government departments in the year to April, BBC analysis has found.
Whitehall departments have included details of personal information losses in their annual financial statements.
Cases included the loss of the National Insurance numbers of 17,000 people and the theft of a laptop with encrypted details of 17,000 Sats markers.
The details of 25 million child benefit claimants vanished last year.
This led to the recommendation that government departments should give details of personal data losses.
The 12-month period to April saw the Ministry of Justice losing information affecting more than 45,000 people, in some cases revealing their criminal records and credit histories.
The Home Office lost the personal details of 3,000 seasonal agricultural workers - including their passport numbers - when two CDs went missing in the post.
In five separate cases, the Foreign Office lost information affecting about 190 people.
And there were six occasions when the Department for Transport misplaced personal data, including three million records of driving-test candidates in May 2007.
The Ministry of Defence lost an unencrypted laptop, a matter on which Defence Secretary Des Brown reported to the Commons in January.
'Torrent of breaches'
The computer contained 620,000 personal records, including bank account and National Insurance numbers.
It also held limited information on 450,000 people named as referees or next-of-kin by would-be servicemen and women.
For the Conservatives, shadow Cabinet Office minister Francis Maude said: "The government's own report admits that there has been a torrent of data breaches in Whitehall. This shows that the government cannot be trusted to protect people's personal details.
"Ministers should think again about its even more risky and intrusive projects such as the identity card database, the all-encompassing children's database and the property database for the council tax revaluation.
"Tougher safeguards are needed to protect the privacy of law-abiding citizens from the government."
A Cabinet Office spokesman said: "The cabinet secretary's review of data handling, published at the end of June, put in place mandatory safeguards to make our information assurance as robust as possible and improve transparency.
"Departments are taking intensive action to improve data security, including extra training for hundreds of thousands of staff, and the problems reported in recently published resource accounts were made public as a result of this new approach."