A memory stick, typically no larger than a pack of chewing gum, can hold vast amounts of data. (CBC)

The British government says a computer memory stick with information on every prison inmate in England and Wales — plus the home addresses of tens of thousands of other criminals — has gone missing.

It is unclear whether the easily pocketed device was stolen by someone planning to use or disseminate the data or was just mislaid. Opposition politicians said taxpayers could end up paying damages to criminals who seek compensation because their privacy was breached.

It is a stunning embarrassment for the government, which promised to tighten procedures after losing 25 million child benefit records last year and details of millions of learner drivers and army recruits this year, London's Daily Telegraph newspaper said Friday.

The Home Office, the department responsible for matters such as law and order, blamed a management consulting firm for the loss.

'Charlie Chaplin could do a better job of running the Home Office than this Labour government.'—Liberal Democrat Nick Clegg

The London-based firm, PA Consulting, has 3,000 employees in offices from New York to Bangalore. It was working for the department on a contract to track offenders through the British justice system.

Home Secretary Jacqui Smith said the government held the data securely but PA Consulting appears to have broken the rules of its contract by downloading it to a memory stick, the BBC reported.

The firm has searched its premises and looked at security video in an attempt to recover the missing item, so far without success, the broadcaster said.

A memory stick, typically no larger than a pack of chewing gum, can hold vast amounts of data, loading or unloading it through a connection found on almost any computer.

In this case, the stick is believed to carry:

• The names and birth dates of the entire 84,000-strong prison population of England and Wales.
• The home addresses of 33,000 people with six or more recorded convictions over the last 12 months.
• Details on another 10,000 criminals designated "prolific and other priority offenders" in a program aimed at "the relatively small number of individuals who cause a disproportionate amount of crime and disorder in our communities."

The Telegraph quoted Nick Clegg, leader of the opposition Liberal Democrats, as saying: "Charlie Chaplin could do a better job of running the Home Office than this Labour government."

Smith, the Home Secretary, called the situation "completely unsatisfactory" and said an inquiry is under way. PA Consulting had no comment, the BBC said.

With filed from the Associated Press