A lost computer disc containing personal details about thousands of justice staff is not thought to have fallen into the wrong hands, a Government minister said.
Data protection minister Michael Wills told the BBC: "We believe the data is not in the public domain and therefore there are not significant risks to security. But obviously we take all steps necessary to mitigate any threat to personal safety."
Justice Secretary Jack Straw ordered an urgent inquiry into the incident, the latest in a string of embarrassing Government data losses including the disappearance last year of two discs containing details of 25 million Child Benefit claimants. Prison officers believe their personal security has been put at risk, and unions are warning that staff may have to be relocated, at a potential cost of millions to the taxpayer, in order to ensure their safety.
The hard-drive was last seen by contractors EDS in July 2007, but it was not until July this year that the private contractor informed the Prison Service and Mr Straw himself did not learn of the loss until it was uncovered by the News of the World.
The 500GB disc contained personal details including the names, dates of birth, National Insurance numbers and employee numbers of 5,000 people employed by the National Offender Management Service, who may include many prison officers as well as administrative staff and other workers.
It was shipped from offices at Mitcheldean in Gloucestershire in July 2007 for testing at a data centre in Washington, Tyne and Wear, and then moved to an EDS facility in Telford, Shropshire. It was only when an employee went to use it on July 2 this year that it was realised that it had gone missing.
In a statement Mr Straw said: "I am extremely concerned about this missing data. I was informed of its loss at lunchtime today (Saturday) and have ordered an urgent inquiry into the circumstances and the implications of the data loss and the level of risk involved. I have also asked for a report as to why I was not informed as soon as my department became aware of this issue. My officials are also in touch with EDS as part of these processes. We take these matters extremely seriously."
A Ministry of Justice spokeswoman added: "We believe nearly all of this data related to financial information - for example, invoices from Prison Service suppliers. However, we believe there is also a limited amount of personal information on around 5,000 NOMS employees including their names, dates of birth, National Insurance numbers and employee numbers."
Prison Officers' Association national chairman Colin Moses said: "We are extremely concerned that not only has this data been lost, but that the Prison Service appear to have tried to conceal this serious breach in security. It is a breach that we believe could ultimately cost the taxpayer millions and millions of pounds, because, if the information lost is personal and sensitive, it may well mean staff having to move prisons, move homes and relocate their families. This obviously will have a significant cost to the taxpayer. We believe that the people who have tried to conceal this serious breach should be brought to account and we are calling on Jack Straw to fully investigate this matter and ensure that justice is seen to be done."
The Ministry of Justice has contacted the Information Commissioner's Office about the incident and will update Commissioner Richard Thomas on the incident on Monday, said a spokesman.