BRITAIN LOCKS up more people than anyone in western Europe. Its prisons, in turn, are grim places. Because politicians like to sound tough to voters on crime, they’ve driven up the numbers of inmates for decades . But no one wants to spend more on cells or guards. The results are bad for all. Prisons are increasingly crowded and violent. Those inside have little chance of rehabilitation. And as prisoners return to wider society, they are ill-suited to be there. It is often said how cruel and counterproductive America’s prisons are. That’s true. But Britain’s ones do not compare well with those in other rich countries either.

Reform is tricky politically because prisons do perform their most popular function: locking away those who pose a danger to the public. Yet there is one big step the government could take, relatively easily, to improve them. Around 60% of prison sentences handed out every year are short, meaning they are anything from just a few weeks to 12 months’ duration. Such short sentences achieve pitifully little, yet do much damage. Arguably, no other public policy so flagrantly contradicts research and common sense.

Short prison stints are chiefly used for non-violent, low-level, repeat offenders, who lead deeply troubled lives. Most have drug, alcohol or mental-health problems—or all three. Many are illiterate and unemployed. Repeat, short spells in prison make their lives more turbulent. They also make prisons more chaotic. New inmates arriving for short sentences are the main conduit for getting drugs into prisons. And putting short-timers with behavioural problems alongside those serving longer spells for more serious crimes causes trouble. Short sentences are a big reason for high turnover among prison workers.

The arguments for curbing short sentences are especially compelling for women. They constitute a small share of those locked up, and most have committed minor crimes. They often also bear the main—or sole—responsibility for children. When they go inside, their children are mostly forced to move, sometimes into care. The children of imprisoned mothers, in turn, are more likely to end in the criminal justice system themselves.

The government should vastly reduce the use of short sentences. It should pass legislation that sets a much higher bar for imprisonment. This would work better than introducing a presumption against short sentences, which might result in some people being put away for longer. A new approach should create a sentencing threshold that means, for example, that shoplifting, the crime that most commonly lands people in prison for short spells, would not carry a custodial sentence.

To make that happen, there also needs to be a better alternative. Community sentences. tend to result in lower reoffending rates than short prison sentences, which is welcome.But they are also imperfect because of poor design and a dysfunctional probation service. Typically they involve a work requirement which is rarely met. A better approach would be to mandate treatment for drug, alcohol or mental-health problems. Magistrates also need better training. Too often they turn to short sentences because they have seen community ones fail. But they fail to grasp that prison fails even more often. They should be taught about alternatives. ■