Prison Service staff are trying to correct errors in a database covering more than 80,000 prisoners after it emerged that thousands of records were wrong, incomplete or missing important information.
The Local Inmate Database System (Lids) holds key information on all prisoners in England and Wales, including how much of a risk they pose to the public, their nationality, ethnic origins and custodial history.
The Prison Service also uses Lids to track where prisoners are, and where and when they are due to be transferred.
A study by the Prison Service's main IT supplier EDS has found that more than 30,000 (37%) offenders did not have a criminal records number, and more than 21,000 (26%) did not have a police national computer number. The database contains records with made-up surnames such as "self-harm", and 194 offenders with no surname at all. More than 1,500 records contain no nationality information.
EDS checked the information in Lids ahead of a project to transfer the data to a replacement database, C-Nomis (the National Offender Management Information System). Prison staff said the information quality problems stemmed from prison officers and other officials entering inaccurate data.
The EDS study gives an insight into the amount of work yet to be done on some public-sector databases to fill gaps and cleanse them of inaccurate data.
Poor data quality is a widespread issue across government. For example, millions of taxpayer records at HM Revenue and Customs are "open" on its databases, partly because of inaccurate records.
A Prison Service spokesperson said the EDS study, although quoted in a notice to staff in February 2008, was 18 months old.
"The position has improved considerably since then and a greater proportion of prisoners currently have their CRO [criminal records] recorded in the Prison Service system," the spokesperson said.
But Prison Service staff question whether there has been a major improvement. They said the system dates back to 1991 when it was due to be replaced within several years, but is still used in nearly all prisons. Lids' Nationalities field, for example, lists East and West Germany as possible choices.
Alex Flynn, spokesman for the PCS union, said his members in the Prison Service "waste large amounts of time" on cross-checking data in Lids against paper records .
The Prisons Service uses Lids for the daily management of the prison population, as well as to generate management information and supply data to ministers and parliament. Last month the Prison Service instructed prison governors, controllers of contracted-out prisons and those receiving prisoners directly from the courts to bring a halt to the entry of inaccurate information.
The notice explained changes in working practices to "ensure the accuracy of Lids data", "ensure data fields are not used for erroneous information", and "prepare for data migration to C-Nomis".
The Lids database has been criticised, in part because information on it is sometimes contradictory. In 2000 a research paper for the Home Office found that where prisoners were being considered for home detention there was a "large minority of cases" in which Lids records were missing or incomplete.
Another research report found that Lids registered no previous offence for a prisoner while noting separately if that individual had previously received a custodial sentence.