The number of young people in custody in England and Wales has reached a record high, prompting warnings of a youth justice system "crisis".
The Home Office said young people were held only as a last resort
The Youth Justice Board, which administers the system, said 3,350 youngsters were being held and action was needed to stop a "meltdown".
Only a handful of beds were free, and children were being held hundreds of miles from their families, it said.
The Home Office said the use of custody for those under 18 was a last resort.
The YJB places young people convicted of crimes and on remand in either young offender institutions, secure training centres or secure children's homes.
It said the rise in numbers had caused an increased risk of self-harm and suicide by youngsters.
It meant difficulties in running crime reduction courses aimed at preventing re-offending.
It also meant increasing numbers were being forced to share cells and youngsters were being transported around the country.
It is against the rules for young offenders to be held more than 50 miles from home.
However, dozens of children and youngsters from London were held as far afield as South Yorkshire and the Scottish borders, said the board.
The board called for more use of schemes in which offenders are tagged and closely monitored in the community.
A spokeswoman said the pressure was greatest on male places in young offender institutions.
Chairman Rod Morgan said action was urgently needed to stop custody for young people going into "meltdown".
"Locking up more children is the equivalent for penal policy of building more coal fired power stations for global warming," he said.
"The likely consequence in the long term is to create more adult career criminals."
The proportion of young people committing crime had fallen, he said, but more were being locked up, partly because of police targets on the number of offences brought to justice.
Custody is usually a last resort
Martin Narey, chief executive of Barnardo's and former director general of the Prison Service, said locking people up had become a media "obsession".
Although custody could sometimes be constructive in getting a child educated and off drugs, "in the sort of numbers the Youth Justice Board are having to lock up at the moment, it is almost always a destructive experience", he said.
"So young children are coming into custody, staying a few weeks, sometimes far from home, losing contact with the home, losing jobs, losing tenancies and coming out more likely to be criminal than before."
But Ann Widdecombe, former prisons minister, said: "The anti-social nature of youth today is a major source of worry."
She said as a minister there had been a shortage of places in custody, which meant a lot of youngsters were still terrorising neighbourhoods when they should have been locked up.
Earlier this month, a nine-hour riot at a young offenders institution in Shropshire saw an entire wing put out of action.
People working with young people said there were more effective alternatives to custody.
David Chater from the young people's charity Rainer said "intensive supervision and surveillance", which consisted of 25 hours a week of education, was much better value for money.
And Shaun Bailey, a youth worker in London, said young people have no respect for authority and it was up to schools and families to take a firmer responsibility about what was acceptable.
The Home Office said about 190,000 young people were dealt with by the police and courts each year but only 4% received a custodial sentence.
However, public protection was its priority and it supported tough sentences for those judged to be a danger to the public, it said.
A spokesman said: "The government is committed to increasing the number of offences brought to justice.
"Where young offenders are concerned, the youth justice system tries to intervene early and turn young people away from the CJS (Criminal Justice System) at every opportunity.
"In the right circumstances, pre-court interventions such as final warnings can be effective at preventing further offending by young people, and provide a mechanism for bringing young offenders to account outside the formal court system."
A rising adult prison population in England and Wales has recently led to prisoners being held in police cells, while the home secretary announced plans to use prison ships.