As of tomorrow, the old Home Office is no more and two new departments, one dealing with national security issues and the other the administration of mainstream justice, will replace it. This is, in theory, a logical reform, as it has long been evident that the Home Office could not cope with the weight of responsibilities that had come its way and that there were potential conflicts of interests within its own walls. Although this division has been pushed through at unusual speed and against the opposition of a series of interests, there are tentative signs that counter-terrorism policy may indeed by improved by this innovation. There are, nonetheless, substantial doubts about whether the same applies to the freshly minted Ministry for Justice, which assumes control over perhaps the most consistently difficult domestic policy issue, namely the Prison Service.

Even before it opens shop formally, the new department has been seeking means to reduce its burden. The prison population today stands at more than 80,000 men and women, a figure that experience suggests will probably rise in the spring and summer months and reach capacity. Lord Falconer of Thoroton, the outgoing Secretary of State for Constitutional Affairs and the incoming Minister for Justice, has floated a series of options for scaling back the numbers in cells, including a softer line on shoplifting and a crack-down on suspended sentences that lead to automatic imprisonment for reoffenders. Some of these proposals have apparently been vetoed by Tony Blair, who does not want to be remembered as the man who permitted a de facto amnesty because of a dearth of prison places. Lord Falconer will have to think again.

His task will not be helped by a separate but related development. For the past two years the courts have been empowered to hand down what are known as “indeterminate” sentences to those who have been assessed as particularly dangerous and sentenced for crimes drawn from a list of 153 offences. Such prisoners are obliged to serve a minimum tariff but will then remain behind bars until the Parole Board decides that they are no longer a threat to society. Ministers seem to have expected that a comparatively small group of especially dubious characters would be affected by this change and would be awarded relatively lengthy minimum sentences.

In fact, a much larger number have been placed in this category. Despite being designated as dangerous, however, half of those recently sentenced have received an initial term of 20 months or less. Prisons will soon find themselves choked with people waiting for the Parole Board to pronounce on whether they have been sufficiently reformed to be released.

One of the worst aspects of the Home Office was that penal policy was frequently dictated more by the availability of berths in prison than a consistent approach towards law and order itself. This created the improper outcome that two people committing the same crime could be treated differently according to what stage in the prison population “cycle” they happened to fall in when sentenced. The task of leadership in this sphere will be made yet harder because the two men who pioneered splitting the Home Office – Mr Blair and John Reid – have already opted for an early release from politics. Lord Falconer is expected to meet a similar, if involuntarily, fate once Gordon Brown has become prime minister. From day minus one, therefore, the Ministry for Justice has an indeterminate appearance to it.