Confidential information on thousands of criminals lost

Sensitive details of thousands of criminals have been lost in the latest major data breach to engulf the Government.

The Conservatives accused ministers of a "massive failure of duty" after it emerged that a memory stick containing details from the Government's secure system for tracking high-profile criminals had been lost by a firm working for the Home Office.

The memory stick contained the names, dates of birth and expected release dates of all 84,000 people now in the prison population, as well the initials of those offenders on a drugs programme, the Home Office confirmed. It also had the addresses and dates of birth of 33,000 prolific criminals – those who have committed at least six serious crimes in the past year. And it also included the names, dates of birth and further information on 10,000 so-called "priority" offenders.

The contents of the stick are based on the Government's Jtrack tracking system, designed to allow police officers to follow offenders when they leave police custody and prison.

Data, which was unencrypted, is thought to have been transferred to the memory stick. This was then lost.

The secure, internet-based Jtrack system gives police forces direct access to information about prosecutions, prisoner-release dates and addresses of "prolific and priority" offenders who have been released. It allows 2,500 officials to track information about offenders.

PA Consulting, a firm carrying out support on the system for the Home Office, is understood to have told the Home Office they had lost the data on Tuesday. Home Office officials contacted police yesterday about the affair. A spokesman said: "We have been made aware of a security breach at the offices of an external contractor involving the loss of personal information about offenders in England and Wales."

A full investigation is being conducted. Police and the Information Commissioner have been informed.

"The data was held in a secure format on the contractor's site. It was downloaded on to a memory stick for processing purposes which has since been lost. The transfer of data on this assignment to the external contractor has been suspended," the Home Office said.

Yesterday, the Tories said the breach could allow offenders to sue for compensation over the affair and warned the data would be highly sought after by members of the criminal underworld.

Dominic Grieve, the shadow Home Secretary, said: "This is a massive failure of duty. What is more scandalous is that it is not the first time that the Government has been shown to be completely incapable of protecting the integrity of highly sensitive data, rendering them unfit to be charged with protecting our safety."

Juliet Lyon, director of the Prison Reform Trust, said prison inmates were supposed to "lose their liberty, not their identity". "It seems extraordinary that a private company should be entrusted with, and then lose, so much confidential data when criminal-justice agencies are still unable to share computerised information between themselves," she said.

Ministers have been buffeted by a string of data losses since the Government faced humiliation when two CDs containing child-benefit data for 25 million people were lost in the internal post of HM Revenue and Customs.

Earlier this summer, the information commissioner, Richard Thomas, took formal action against HMRC and the Ministry of Defence over "deplorable failures" involving data breaches. In April, he revealed that he had been passed "alarming" details of almost 100 data breaches.