If the public are losing confidence in the Government’s ability to deal with crime and antisocial behaviour, they are right to do so. The system is an arbitrary and illogical shambles.

As this newspaper reports today sentences are being slashed by prison governors, thanks to chronic overcrowding. To take one example, a criminal facing 42 days, sentenced on a Friday, could find himself heading home immediately. His sentence would be automatically cut in half, he could lose another 18 days due to an early release scheme, and then lose the final three because prisons do not release inmates at weekends. Six weeks in jail would instead become a trip home, with a resettlement grant as an added bonus. Were this not so terribly unfunny, it would be very funny indeed.

Why are criminals not being sent to jail? The prime reason is that there are simply not enough jails. There are not enough jails because the Government has not stumped up enough cash to build them. The collapse of Britain’s economy is not the only way that Gordon Brown’s tenure as Chancellor has returned to haunt him since he moved next door.

To be fair, this is a problem inherited from the Conservatives. The last Conservative Home Secretary, Michael Howard, was of the view that “prison works”, but his Government was far more keen on sending people to jail than it was on building jails to house them.

Tony Blair pledged to be “tough on crime, tough on the causes of crime”, but his Government was equally ineffective when it came to providing the infrastructure.

In part, this was due to the ideological schism at the heart of new Labour. As Chancellor, Gordon Brown considered the former part of Mr Blair’s slogan to be questionably right-wing and preferred to spend money on the latter. Thus, even as Mr Blair’s policies caused custodial sentences to increase, long-term rehabilitation rather than short-term punishment remained Mr Brown’s financial focus. Prison numbers continued to grow, but prisons did not.

Louise Casey, the Government’s neighbourhood crime adviser, believes that people working within the criminal justice system are often too sympathetic towards offenders. Perhaps her criticisms could go right to the top. When Mr Brown became Prime Minister, responsibility for Mr Blair’s flagship respect agenda (principally antisocial behaviour) shifted from the Home Office to the new department of Children, Schools and Families, under Ed Balls. Again, there was more emphasis on prevention, rather than enforcement. At this year’s Labour Party Conference, Mr Brown outlined his own plans to crack down on antisocial behaviour. In his tone, at least, the Prime Minister appeared to be belatedly accepting that justice sometimes requires not just carrots, but also sticks.

Obviously, rehabilitation is important over the longer term. Britain has a high prison population because it has a high number of crimes. Too many criminals reoffend, and too many of their children join them (see page 8). In the short term, we still have too few cells, with sentences rendered farcical. What can be done?

There are foreign prisoners in our jails, who could be repatriated. There are minor criminals, mental health patients and drug addicts, who could be better dealt with elsewhere. In this, however, sentencing should not have a major role. We need to work out the appropriate sentence and then plan prison places accordingly, not the other way round. Judges should not be deciding punishments on the basis of what we can afford. Most importantly, when a sentence is passed, it must be carried out. If somebody is jailed, to jail they must go. Public confidence demands it.