The Ministry of Justice (MoJ) has admitted it lost the personal details of 45,000 people over the past financial year.
The data was lost as a result of nine different incidents, says the MoJ's annual resources report.
The worst incident, last June, saw the loss of names, addresses and some bank details of 27,000 people working for suppliers to the MoJ. The details were held on computer disks.
And this January, an "inadequately protected" laptop in "a secured government office" went missing. The laptop contained the names, dates of birth, addresses and offence details of 14,000 fine defaulters. In a fifth of the cases, the lost records included people's National Insurance numbers.
In a different incident, MoJ officials mislaid another "inadequately protected" laptop which contained the job applications of 13 people who were applying for judicial posts.
Other data loss incidents are believed to have involved mislaid USB memory sticks.
Although the police were informed about six of the nine data losses, 30,000 of the 45,000 people affected were not told of the data losses.
The MoJ says it carried out a risk assessment for each incident to decide who should be notified.
Government data breach: