Dominic Lawson: The most effective way to reduce crime is to put more criminals in prison

The answer to overcrowding is not to empty the prisons. It is to build new ones

Whenever a minister announces a "new policy initiative" there is one question that needs to be asked before any other. That question is:"Why is he telling us this now?" So we should apply this test to the Home Secretary, Charles Clarke, who yesterday unveiled "A Five Year Strategy For Protecting The Public And Reducing Reoffending". If you read this document, you will see almost at the very beginning the decision of the Government to ensure "better parole decisions, with the Parole Board putting the safety of the public first". Well, that's a marvellous idea, putting the safety of the public first. However did they come up with that?

The answer is that Andrew Bridges, Her Majesty's Chief Inspector of Probation, is just about to publish his report into the appalling catalogue of official blunders which led up to the release of Damien Hanson only half way through a 12-year sentence for attempted murder. Within weeks of his release by the Parole Board, as a "low risk", Hanson murdered the banker John Monckton and attempted to murder his wife, Homeyra, in a highly-planned, premeditated assault.

Perhaps, since John Monckton was my wife's cousin, I may be overemphasising the Government's own obsession with the case. But I don't think so: until his attention was diverted by the events of 7/7, The Attorney General, Lord Goldsmith, had planned to open for the Crown vs Hanson at the Old Bailey. Charles Clarke has, I believe, already seen Andrew Bridges' report and is apparently shaken by what it reveals about the workings of the Parole Board and the Probation Service: yesterday's "Five Year Strategy For Protecting the Public" was his pre-emptive response.

While Mr Clarke's main aim is to reassure the electorate that the criminal justice system is protecting the public, I'm afraid that the overriding theme of his report - that alternatives must be found to prison in the crime prevention business - is the same failed policy of the past. The Home Office, as an organisation, has still not accepted that the most effective way of reducing crime is to put criminals in prison. There was great internal resistance when the last Tory home secretary imposed his "prison works" strategy, and great perplexity among the bulk of the criminological establishment when "prison works" worked. The extraordinary reduction in crime in recent years across the US is partly attributable to a similar policy. It may well be that the reoffence rate is unacceptably high when prisoners are released from incarceration: but the rate of reoffence by those who are given a non-custodial sentence is scarcely any less high, with the added punishment - for the public, that is - of hundreds of thousands of offences committed which would not have taken place at all if the original offenders had been on the inside.

I am well aware that the British prison population is at a record high, and that we have the highest prison population per capita in Europe. But these points do not seem to me to amount to an argument. First of all, while it is true that we imprison more people than our European neighbours, our ratio of prison sentences per criminal conviction is by no means the highest in Europe. And if we assume, as many experts in the field do, that the amount of burglaries committed for each burglar actually found and then given a prison sentence is something like 100 to one, then you begin to get a sense of the reduction of human misery that could be achieved by a more rigorous policy. So I don't think that the answer to prison overcrowding is to empty the prisons. It is to build new ones. What little I remember of my economics course at university tells me that serious crime can be expressed as a demand for prison, and that to reduce the supply will only increase that demand, not diminish it. Or if you prefer a different sort of equation, all markets are a balance between fear and greed. In crimes of theft, fear of imprisonment is the main countervailing force to a greed which otherwise is checked only by conscience.

Nor is it the case that the prison population is going up purely because of incarceration for offences of a relatively unthreatening nature. In the Home Office document released yesterday, it was fascinating to see that in the year to November 2005, the overwhelming proportion of the increase in the prison population was attributable to convictions for "violence against the person". The numbers of people in jail for robbery or burglary without violence was actually in decline.

There are, admittedly two categories of prisoner which have expanded rapidly in recent years, and Charles Clarke is right to believe that these need to be reduced. The first category is foreign nationals. Did you know that our prisons contain 1,742 Jamaican nationals - in other words, more Jamaicans than are in prison in Jamaica? But it's understandable that the Home Office is unwilling to send these drug mules back to the Caribbean if it fears they will be bouncing back with more skunk for sale on the next plane into Heathrow. The second category of prisoner which needs to be reduced is that of the mentally ill. And having praised the last Conservative government for one aspect of its criminal policy, that administration should only be condemned for its introduction of the policy of closing down the country's asylums - otherwise known as "care in the community"- in the fatally fashionable view that these poor people were capable of looking after themselves.

It was also the last Conservative government which introduced the policy dictating that anyone sentenced to a term of four years or less should be released after half his sentence, regardless of his conduct. When I asked someone involved in that decision about the reasoning behind it, he said it was because the Home Office was terrified of prison riots. Or in other words, the Government was actually intimidated by the criminals it had incarcerated, and preferred to shift the risk of dealing with such people onto the unwitting public. I suspect that the public also doesn't know that not only are all prisoners, including the most dangerous, eligible for parole after half their sentence: they are released automatically after serving two thirds of their sentence, regardless of the views of the Parole Board or the probation service.

With that in mind let us consider the case of prisoner Abu Hamza, who on Tuesday was sentenced to "seven" years for crimes such as incitement to commit murder. Hamza had been on remand for 18 months before his trial. That, believe it or not, counts as double time under statutory regulations. So he has already "served" three years. And since he is eligible for parole after half his sentence, he may be entitled to release in six months' time. Does that make you confident in our system of justice?

d.lawson@independent.co.uk