A computer company delivering the national identity card scheme was frantically hunting yesterday for a lost computer drive containing 5,000 personnel files, including the private details of prison officers.

The data storage device, little bigger than a paperback book, was last seen more than a year ago in a storeroom of EDS, one of the world’s biggest new-technology consultancies.

Jack Straw, the Justice Secretary, the Prison Officers’ Association (POA) and the Information Commissioner knew nothing of the loss until a Sunday paper found out.

David Davis, MP, the former Shadow Home Secretary, who forced a by-election on civil rights, told The Times the incident showed that neither ministers nor private contractors could be relied upon. “Yet again it demonstrates the astonishing lack of discipline, not just on the part of the Government but on the part of the people who will be responsible for the integrity of the new ID card system,” he said.

The loss threatens Mr Straw’s reputation for competence, the credibility of the American private company and confidence in the ID card scheme that it is due to run. Ministers have insisted on pressing ahead with ID cards in spite of a string of serious failures. A leaked memo shows that senior Prison Service staff have known for months about the scandal. Ministers say that they were kept in the dark.

The hard drive was last seen in July 2007. When an EDS employee needed to retrieve its contents on July 2 this year, the device had vanished.

It is unclear whether actual addresses were included but criminals can easily trace where a prison or probation officer lives using the information that has been lost. Prison officers’ leaders immediately threatened to go on strike. Colin Moses, chairman of the POA, said: “During the past two to three months senior members of the POA have met with the minister, his adviser and leaders of the Prisons Board and no one has seen fit to mention this security breach.”

EDS was blamed for the tax credits disaster when low-income families were overpaid £2 billion and then told to pay much of it back. A spokesman for the Ministry of Justice said that Mr Straw had asked for an urgent report.

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