For the past year, I have had the privilege of serving as the High Sheriff of Greater London. In this role, I have visited prisons, sat in on court proceedings, talked to many judges and police, including the Metropolitan Commissioner of Police, visited the probationary service and NACRO and attended conferences on crime.

A disproportionate share of crime is committed by young people, especially young males. It is believed that about half of total crime in this country is now committed by males aged between 10 and 25. Offenders under the age of 18 commit seven million offences a year - more than a third of the total.

In 1995 217,500 young people aged 10 to 20 in the United Kingdom were cautioned or found guilty of indictable offences with 15,000 young offenders being sentenced to custody. It costs pound;25,000 a year to keep someone in prison with a total budget of pound;1.5 billion for the 60,000 currently in prison. Crime is therefore a very expensive business for the taxpayer.

Secondly, there is a very high rate of re-offending for young offenders. Depressingly, seven out of 10 prisoners aged 15 to 21 have re-offended within just two years after being released. Meanwhile, 5 per cent of young men commit two-thirds of the crime committed by their age group.

What can be done to prevent the rise in crime by young people?

We need to learn more about the causes of the rise in the number of young offenders. Research indicates that many young offenders share common origins and traits. Most are males. Many have been excluded from school or suffer from inadequate parenting, have inadequate reading and numeracy skills (and thus find it difficult to find jobs), and come from single-parent families living in the inner-city stress areas.

Many have become involved in drugs or alcohol abuse. Nearly all have very low self-esteem and many mix with others who offend. There is a clear link between poverty, unemployment and a general disenchantment with society which leads to drug abuse and so criminalises many who would not otherwise be offenders.

The Audit Commission report Misspent Youth said that any strategy for tackling youth crime must address the behaviour of different groups of young people: persistent offenders; young offenders who have yet to develop an entrenched pattern of offending; first-time offenders. Young people at risk, such as those who are excluded from school, must be discouraged from offending in the first place.

Measures which we should consider include: requiring parents with children who offend to take compulsory counselling on good parenting; better packages of remedial education and counselling for young people excluded from schools including improving the special referral units for those who are frequently excluded from school.

We should give some categories of under-16s with behavioural problems statemented or special pupil status. Good schools with an caring, disciplined ethos might be prepared to admit a limited number of pupils excluded from other schools, bearing in mind there would be additional funding to pay for the extra costs.

The policy on excluding pupils from schools should be reviewed to restrict permanent exclusion to only the most serious cases involving violence. Adequate provision should be made for those pupils who are excluded, since otherwise they become the next generation of young offenders.

More must be done to stop the activities of the drug-dealers in selling drugs to young people. We should place a cordon sanitaire round each school through the installation of surveillance cameras and intensive police action. This would discourage the sale of drugs to pupils. We also need to improve the standard of good health and anti-drug education in schools.

A more efficient and streamlined procedure needs to be developed for bringing young offenders to court. The recent proposals to lower the age at which young offenders are deemed capable of knowing the difference between right and wrong from 14 to l0 seem sensible. But more needs to be done. A national computer record of young persons at risk of offending could be created and social services departments could be required to monitor the progress of potential young offenders - that is those who have been cautioned or excluded from school.

At present there is a considerable delay in bringing to trial young people on remand. Feltham Young Offenders Institution now has more than 600 young men held on remand - three times the planned level. Typically these young people are waiting up to six or seven months to be tried and their presence is preventing crucial rehabitation work for the young offenders who have been sentenced. The procedures for bringing young offenders to trial should be reviewed and delays reduced. The implications of putting 15-year-olds who are accused of a first offence on remand into an institution such as Feltham are chilling, especially if their stay there is a lengthy one. In Scotland, those arrested and held on remand must be tried within 101 days or be released.

We should replicate or expand some of the proven measures which have been successful in rehabilitating young offenders. Such initiatives as the Sherborne House Day Centre run by the Inner London Probation Service in Southwark should be replicated elsewhere. Under the Sherborne House scheme, judges may, if they wish, send persistent young offenders aged 16 to 20 to an intensive 4.5 day-a-week, 12-week programme. The scheme is not open to offenders of serious violent crimes.

During this period, offending behaviour is analysed in rigorous and often traumatic group discussions. Offenders are sent to apologise to their victims. There is considerable counselling as well as skill training. Discipline is strict and those refusing to conform or who do not attend regularly and punctually are returned to the courts for sentencing.

While tracking data is currently imprecise, there are indicators that a high proportion - perhaps half - of those who spend three months at Sherborne House do not re-offend. Bearing in mind that the equivalent annual per capita cost of the Sherborne programme is only pound;2,000 (compared to the pound;25,000 of prison), there is an enormous potential saving to the taxpayer if more was spent on rehabilitating young offenders rather than sending them straight to prison to become the hardened criminals of the future, many of whom will be in and out of prison all their lives. Panorama recently estimated that a single male young offender could over his lifetime cost the taxpayer pound;1 million.

The community service orders are also a cost-efficient and effective method of turning young offenders into productive citizens. Such schemes bring offenders into contact with the victims of crime and teach them useful skills which can lead to gainful employment.

The probation service should be encouraged and enabled to build on these successes. The investment required will prove to be cost efficient as well as helping to reduce crime and protect the quality of life in our cities. Currently less than pound;500m is spent on the probation service - only 5 per cent of the total cost of the judiciary.

What we cannot do is to ignore this problem and encourage the growth of a disillusioned under-class of young offenders in our cities who have little prospect for gainful employment and who will cost us dearly - in terms of both the damage they do and the cost of apprehending and restraining them.