The Home Office refused to comment on reports suggesting ministers covered up failures in a scheme to track high risk offenders including paedophiles.
Tracking is meant to address community safety fears
Reports suggest the £2.5m project using satellite tracking was hit by a number of technical hitches as signals were blocked by trees, clouds and buildings.
The Mirror said it had seen leaked documents suggesting ministers were advised the public should not be told.
A Home Office spokesman said: "We never comment on leaked documents."
In its report the Mirror quoted advice to Home Secretary Charles Clarke saying: "We have sought not to publicise the pilot scheme ... due to the risks of negative media coverage of the poor results."
Prison without bars?
The department's press office had "strongly advised against any publicity" and the memo went on to warn Mr Clarke he was "not prepared to take those risks".
"We recommend that you delay any media announcement until interim results significantly improve," it added.
Mr Clarke's predecessor, David Blunkett, said the pilot scheme was a "prison without bars" when he launched it in Hampshire, the West Midlands and Manchester last September.
In Manchester the technology was used for sex offenders, in Hampshire and the West Midlands for people who committed offences of domestic violence and for prolific offenders.
Up to 120 offenders were due to be fitted with satellite tags which were claimed to pinpoint their exact location 24 hours a day.
The leaked report to the home secretary said: "If the subject is between tall buildings, a canyon effect can prevent accurate location.
"Leaf cover and cloud cover can mask the strength of the signal.
"Location cannot be obtained on planes, some intercity trains and the Underground.
"Location is usually lost inside buildings."
No early releases
A statement released by the Home Office on Thursday stressed the pilot projects were not just sex offender programmes and that tracking was "not a replacement for any other form of supervision".
It added: "Offenders being tracked have either received a community order, or in most cases, been released on licence from prison. They have not been released early from prison."
The department acknowledged the "technology is not perfect" but added that technological advances could mean there was an increased likelihood of obtaining a signal in "adverse conditions outside".
"In the last few months the number of those on tracking has increased substantially as confidence has grown amongst practitioners. An extension to the scheme was proposed to build on that progress and ensure sufficient data was obtained from the pilot."
A full evaluation is being carried out and is due to report in March 2006.
The system features electronic ankle tags with a wireless connection to a mobile phone which is suppose to be carried by offenders at all times and sends back co-ordinates to a tracking station.
If the phone is separated from the tag it sets off an alarm, which is also supposed to alert the authorities if a criminal approaches a forbidden area - for example a paedophile going near a playground.
In May 2004, Mr Blunkett said satellite tracking would mean "a more secure system and people can rest more securely in their beds".