With Britain's prisons system at breaking point, the Lord Chief Justice, Lord Phillips of Worth Matravers, talks of his concerns over longer sentences for offenders.

In a speech in 1910, Home Secretary Winston Churchill, told Britain: "The mood and temper of the public in regard to the treatment of crime and criminals is one of the most unfailing tests of the civilisation of any country.

"A calm and dispassionate recognition of the rights of the accused against the State, and even of convicted criminals against the State, a constant heart-searching by all charged with the duty of punishment, a desire and eagerness to rehabilitate in the world of industry all those who have paid their dues in the hard coinage of punishment, tireless efforts towards the discovery of curative and regenerating processes, and an unfaltering faith that there is a treasure, if only you can find it, in the heart of every man - these are the symbols which in the treatment of crime and criminals mark and measure the stored-up strength of a nation, and are the sign and proof of the living virtue in it."

If those words were uttered today, he'd be accused of being soft on crime and more concerned for the criminal than for the victim. In fact, Churchill received much criticism, but his approach marked an appreciation that an important aspect of sentencing was rehabilitation.

In the 40 years that followed, prison numbers remained relatively modest, probably because of the two World Wars. Many of the young men who might have found themselves the object of the criminal justice system were called up, subjected to military discipline and given a legitimate outlet for any tendency to violence.

At all events, in the period before the Second World War there were usually about 10,000 prisoners in England and Wales. In 1946 there were about 15,000 and, since then prison numbers have risen steadily, so that in 1961 there were nearly 30,000 in prison and today there are nearly 80,000. Much of this period has seen serious overcrowding, leading to understandable resentment by prisoners and problems with discipline. It also renders much more difficult the implementation of current policy, which aims to rehabilitate prisoners so that they will not re-offend.

I have visited a number of prisons and have been impressed by the dedication with which the Prison Service attempts to give effect to this objective. Their efforts include education and drug treatment.

A large proportion of the prison population suffers from some form of mental illness or disability, and treatment is provided by the National Health Service. It is the aim of the National Offender Management Service that each offender will receive individual and tailor-made management until his release. But these excellent aspirations will be destroyed if prisons are over-crowded.

Overcrowding results in prisoners finding themselves incarcerated wherever there is a vacancy - often far away from their social and family links.

Overcrowding results in prisoners being shuffled from one prison to another, so that if they leave for a court hearing they may be returned to, not merely a different cell, but a different prison from that which they left.

The causes of the horrifying rise in prison numbers are not all that easy to analyse. In 2002, a report showed that half of all prisoners are at or below the level expected of an 11 year old in reading; in numeracy two-thirds reach that level; two thirds were unemployed before imprisonment. Nearly half of sentenced prisoners were excluded from school; the same proportion ran away from home. The majority of men and almost three-quarters of women in prison have no qualifications. A quarter of men and a third of women admit to using heroin or crack cocaine in the year preceding their imprisonment. 72 per cent of men sentenced to prison have two or more mental disorders.

One way to reduce prison numbers is to deal with deprivation, but there is another factor that contributes to prison overcrowding.

We send more people proportionally to prison, and for longer, than any other country in Western Europe. Furthermore, over the last 20 years there has been a marked increase in the length of the average sentences imposed for serious offences: drug offences, criminal damage, violence and burglary.

Finally, there has been a massive increase in sentences of under 12 months.

I have two personal concerns about these statistics. The first relates to the increasing length of sentences imposed for serious offences. The Criminal Justice Act 2003 requires a court, when imposing a sentence of imprisonment, to impose the shortest term that is commensurate with the seriousness of the offending. This requires the court to evaluate, in terms of length of sentence, the particular offence for which a defendant is convicted.

This is no easy matter. If you have never experienced imprisonment it is very difficult to estimate the punitive effect of a month, or a year, or ten years deprived of one's liberty.

Some elements of the media are inclined, however, to make light of sentences of imprisonment - to speak of defendants being permitted to 'walk free' after only five years inside. I am inclined to think that to be confined in prison for five years is a very weighty punishment indeed.

That is not to say that I do not recognise there are certain crimes which require a lengthy sentence, but I detect on the part of such publications an incitement to the public to exact vengeance from offenders. Media pressure such as this cannot fail to have effect on the public, on politicians and on judges.

The 2003 Act lays down a scale for determining the minimum time that those convicted of murder will serve in prison and, in accordance with that scale some murderers are being sentenced to a minimum of 30 years, or even full life terms. Lengths of sentence reflect, to a degree, public sentiment and, as chairman of the Sentencing Guidelines Council, I am in part responsible for them. But I sometimes wonder whether, in 100 years' time, people will be as shocked by the length of the sentences we are imposing as we are by some of the punishments of the 18th Century.

My other concern is about the short sentences of imprisonment passed in relation to less serious offences. Statistics show that about two thirds of those who receive a short terms are re-convicted within two years.

It is government policy that imprisonment should be reserved for serious offenders, in particular those who pose a danger to the public, and that other forms of punishment should be meted out to the less serious offenders. Fines and community sentences are the most common alternatives to imprisonment.

The National Offender Management Service's plans for the future show a continued commitment to rehabilitation, both in prison and in the community. But some of the media, and some sentencers, are sceptical as to whether community sentences provide adequate punishment and whether they are effective in preventing re-offending.

I am well known as supporting community sentences as an alternative to imprisonment in appropriate cases. I have witnessed 'community payback', drug treatment and domestic violence courses. They are not a panacea, but I believe they offer a better chance of preventing re-offending than short spells of imprisonment and can leave room in the prisons for effective intervention for those whose crimes require detention. But if community sentencing is to work it must be properly resourced and the public must be educated to accept it does indeed constitute punishment.

I hope that the years to come may see a general appreciation of the importance not merely of punishing criminals but of attacking the causes of their criminality.