But the government's £63m campaign to stop young offenders developing into life-long criminals has been dismissed by the opposition as "meaningless".

Conservative home affairs spokesman James Clappison said young offenders' institutions were already overstretched and could not cope with more children.

Writing in the Sunday Express, Mr Blair says: "For too long, there's been a view that most youngsters would grow out of wrongdoing and those who didn't couldn't be changed.

Tony Blair: Seven million crimes a year by 10 to 17 year olds

"It's an attitude which led to a staggering seven million crimes by youngsters between the ages of 10 and 17 every year."

The existing system failed to tackle the scale of youth crime and allowed a long gap between arrest and trials, he said.

"This sent exactly the wrong message. They were left with the mistaken belief that no-one cares about their crimes any more than they do themselves."

This led to Labour making the "early pledge" to cut by half the time between arrest and sentencing.

The new Youth Justice Board is to receive £13m for 80 local initiatives to monitor young people on bail, Mr Blair writes.

"It will help reduce crime by curbing the bail bandits - youngsters who see arrest as an excuse for a new crime spree."

He said a further £50m would be spent on local initiatives to prevent youth crime.

"They will enable early intervention and offer support and counselling. And for the first time the courts will have the power to send children aged between 12 and 15 to local authority secure accommodation."

Many young offenders continue to commit crime on bail

But the Tory home affairs spokesman said only six secure accommodation places for young offenders had been created under the Labour government.

"This is clear evidence that Labour's tough words are simply not matched by their actions," said Mr Clappison.

"Blair's recycled announcement today is meaningless as there are simply not enough secure places to accommodate young offenders.

"Whilst we would welcome any sensible measures designed to reduce crime amongst young people, any such policies must address the problem, not be designed purely to grab headlines one day and be forgotten the next."

Director of the National Association for the Care and Resettlement of Offenders, Paul Cadavino, said powers to lock young people up in local authority accommodation could be the wrong answer to the problem.

"Courts can already remand children to secure accommodation if the local authority applies for a secure accommodation order," he said.

"The government is now empowering magistrates to make such orders without a local authority application.

"There is a risk that the new powers could lead to the locking-up of children for whom bail support or remand fostering would be a better option."