Personal details relating to thousands of criminals have been lost in the latest in a line of Government data blunders.

Personal details relating to thousands of criminals have been lost in the latest in a line of Government data blunders.

The Home Office said a computer memory stick containing information on around 10,000 prolific offenders had been lost by a contractor.

PA Consulting warned the department on Monday that the stick - which also contains data on all 84,000 prisoners in England and Wales - might be lost.

And tonight the Home Office admitted it was missing.

A spokeswoman 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 spokeswoman also said the stick included information from the Police National Computer of around 30,000 people with six or more convictions in the last year.

Opposition parties described the loss as a "massive failure of duty" and accused the Government of being unable to keep any information safe.

Shadow home secretary Dominic Grieve said taxpayers would be "absolutely outraged" if the loss led to big compensation payouts to the criminals involved.

Mr Grieve 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.

"The British taxpayer will be absolutely outraged if they are made to pick up the bill for compensation to serious criminals."

And Liberal Democrat leader Nick Clegg argued the loss was evidence that the Government could not be trusted to run an ID cards scheme.

Mr Clegg said: "Charlie Chaplin could do a better job running the Home Office than this Labour Government.

"After tonight's revelation people will start wondering whether ministers are capable of keeping any data safe anywhere in the country.

"The Government will no doubt seek to blame private contractors, but the rash of data losses over the last two years confirm that there is something much more worrying at stake: this Government cannot keep any information safe.

"If this Government can't keep data about criminals and the guilty safe, why on earth should we trust them with the data of millions of innocent Britons in an ID card database?"

The Government has been hit by a series of data loss revelations over the last year.

Last November, Chancellor Alistair Darling revealed that the details of 25 million individuals - including bank accounts and National Insurance numbers - had been lost when discs containing child benefit data went missing in the post.

In December, Transport Secretary Ruth Kelly told MPs that information relating to three million learner drivers had been lost when a hard drive was stolen in Iowa.

Later that month HM Revenue and Customs admitting losing the details of 6,500 private pension holders.

This year the Ministry of Defence said more than 100 memory sticks and 650 laptops - some containing secret information - had been lost or stolen since 2004.

That came after sensitive files relating to terrorism, drugs trafficking and money laundering were found on a train.

Nobody from PA Consulting was available for comment.

The Home Office said names and expected release dates and dates of home detention curfew for all 84,000 prisoners were contained on the stick.

In addition, the names, addresses and dates of birth of the 30,000 people with six or more convictions are included in the lost data, as are the names and dates of birth of the 10,000 offenders regarded as prolific.

There are also the initials of people on drug treatment programmes.

PA Consulting had the data as part of research it was carrying out for the department on tracking offenders through the criminal justice system.

It is not yet known how the stick went missing, though it is not thought to have been from a break-in at the company's London offices.

After warning on Monday that the stick might have gone missing, PA Consulting told Home Secretary Jacqui Smith on Tuesday that it had definitely vanished.

The company has a number of contracts with the Home Office, and it is understood that these will be examined in light of the data breach.

They include a three-year contract for the support and maintenance of JTrack, the Government's system for tracking and managing prolific and priority offenders.

In 2004, it won a two-year contract worth around £19 million to work on the ID cards programme - working on the design, feasibility testing and procurement issues.

Juliet Lyon, director of the Prison Reform Trust, said: "People are sent to prison 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."

Officers from Scotland Yard's Specialist and Economic Crimes Unit have been brought in to try and establish what has happened to the stick.

But a spokesman from the Metropolitan Police revealed that they were only asked for help by PA Consulting today.

And he hinted that the stick had been mislaid by an individual.

The spokesman said: "Officers from the Specialist and Economic Crimes Unit are currently meeting with PA Consulting to review the circumstances of the loss by their member of staff. There is no investigation at this stage.

"Today, August 21, we were asked to provide assistance to PA Consulting to review the circumstances of the loss of data."

The review means police are not currently treating the loss as a crime at this stage, and will look to see how the company might protect against similar losses in future.

The Information Commissioner's Office said "searching questions" would need to be answered.

David Smith, Deputy Commissioner, said: "It is deeply worrying that after a number of major data losses and the publication of two government reports on high-profile breaches of the Data Protection Act, more personal information has been reported lost.

"The data loss by a Home Office contractor demonstrates that personal information can be a toxic liability if it is not handled properly and reinforces the need for data protection to be taken seriously at all levels.

"It is vital that sensitive information, such as prisoner records, is held securely at all times.

"The Home Office has informed us that an internal investigation is being carried out into the data security arrangements between the Home Office and its contractor, PA Consulting.

"We expect the Home Office to provide us at the Information Commissioner's Office with a copy of the report and its findings. We will then decide what further action may be appropriate.

"Searching questions must be answered about what safeguards were in place to protect this information."