During 1997, there were 102 children aged between 10 and 17 who were classed as persistent offenders after being convicted in court three times within three years.

But by 2007, that figure rose to almost 340, a rise Supt Pete Glover, of the Northamptonshire West criminal justice unit, put down to huge growth in the county over the past decade.

He said:"There has been a rise in the number of persistent young offenders in the county in the last 10 years, partly due to demographics.

"We are one of the only places in the country that has an increasing number of young people and this can only continue with the planned expansion of the county.

"A great deal of work is completed with young people and their families who have been identified as moving in a criminal direction and as a result, the number of crimes committed by young people in the county is falling, as is reported crime."

The Government figures were released in a written answer to a question from the shadow minister for home affairs David Ruffley and show the number of young offenders has risen consistently, year on year, for a decade.

But they also revealed that of all offences brought to justice during the 2006/07 period, only 0.62 per cent were attributed to persistent young offenders.

Supt Glover added: "Persistent young offenders are aged between 10 and 17 and have been found guilty in court on three or more occasions within three years.

"In Northamptonshire we do not criminalise the young, we criminalise criminals who have been found guilty by a court of law."

The county's Crown Prosecution Service (CPS) has also revealed that cases involving youth offenders in Northamptonshire now take an average of 47 days to complete, compared with 103 days at its height in April 2006.