3 Investigates: Tagging Criminals airs on Monday
There is no evidence the electronic monitoring of criminals reduces re-conviction rates, the Home Office has admitted.
BBC Three's Raphael Rowe meets criminals with electronic tags, and investigates the companies that are supposed to be keeping a close eye on them.
Electronic tags are designed to keep criminals in their homes under curfew and to stop them going out to commit crimes.
There are currently 10,000 criminals on a tag. Most of them are on the Home Detention Curfew scheme, which allows prisoners to leave jail early.
The private companies that monitor these offenders make millions of pounds through government contracts.
The British government says it wants to double the number of offenders on electronic tags by 2008.
Seen as a tool to tackle prison population numbers, juveniles, terror suspects and custodial battles, Labour wants this virtual prison to be the new solve-all sentence.
So does the tag work?
I embarked on a four month journey to find out more from the criminals, the victims, and the employees of the companies.
I uncovered confidential documents that revealed the tragic consequences of a tagging company's failure to act on a repeat offender.
I began my journey by meeting several tagged offenders, all of whom have their own story to tell about how their tags are really working.
Some admitted repeatedly committing crimes while wearing the tag and others claimed to have beaten the system.
One young man I met told me that he took his tag off.
Although he was supposed to be at home under curfew, he was in fact "robbing cars, going to parties, drinking".
The tagging company took no action and he was free to do what he liked for a month.
Another young criminal told me that he couldn't see how a tag would stop him committing crime.
"In at seven o'clock, what's that? How is that going to stop your crime?" he said.
Their weary parents were not confident that tags were a sufficient punishment for their children.
Many of the parents I spoke to would rather see their child locked up in prison.
"Matthew should be in prison, he is my son and I think a proper sentence in prison would do Matthew the world of good, more than the tag," one told me.
I spoke to current and ex-employees of the tagging companies. Talking to these people made me aware of the widespread technical problems with the equipment.
I uncovered a catalogue of technical failures and control centre mismanagement that lead to criminals being left unmonitored and free to breach their curfews.
One former employee said the system was so mismanaged that recently released offenders would phone up asking why they had not been tagged yet.
"They've said, 'When're you gonna come round and put the tag on? I've just come out of prison yesterday: I'm meant to be tagged.'"
I spoke to experts to ask them what research says about tagging. "It says what you would expect it to say, which is that it has no basic impact on crime, on re-offending."
When we challenged the Home Office it admitted that there was no research to show that tagging criminals stops re-offending.
3 Investigates: Tagging Criminals will be broadcast on BBC Three on Monday 21 March at 2000 GMT