Electronic tags were brought in to help combat anti-social behaviour
The number of young offenders ordered to wear electronic tags in England and Wales has seen a steep rise.
Nearly 20,000 15 to 17-year-olds were tagged last year, up 40% in three years, figures show.
But government statistics also reveal that more than half of those teenagers breached their restrictions, either by removing the tags or breaking curfews.
The Tories accused ministers of failing to enforce the scheme but the Ministry of Justice said tagging was effective.
Electronic tagging of people as young as 10 was introduced to deal with the problem of youngsters who made the lives of others a misery through anti-social behaviour.
It was also seen as a cost-effective alternative to custodial sentences.
A Ministry of Justice spokeswoman said: "Electronic monitoring provides the courts with a credible alternative to custody.
"It can be used alone, or as an enhancement to other community interventions.
"Curfews introduce regularity into what are often chaotic lifestyles. They enhance supervision and can disrupt the pattern of offending behaviour."