The decision by Scotland's chief constables to set up a joint central unit to deal with major crimes, including serial murders, other unusual homicides and complex rape cases, is more than an example of inter-force co-operation. It is a pre-emptive strike in a war of attrition between those who want more services to be provided centrally and the senior officers of the eight forces who believe it is essential that each force provides an autonomous service for its area.

There are obvious advantages in being able to call in quickly officers with highly specialised skills from other forces. The still-unsolved murder of the banker Alistair Wilson on his doorstep in Nairn in November 2004 is the classic example of a murder whose unusual features were out of the experience of a small, largely rural, force.

The current arrangement of eight police forces, based on the geographical areas covered by the previous regional authorities, has a major flaw in that one force, Strathclyde, is far larger than any of the others. However, the provision of centralised services to extend the capacity of the smaller forces has proved highly controversial. The Scottish Police Services Authority (SPSA), set up last April, provides centralised training and forensic services and will take over IT next month, but it also oversees the Scottish Crime and Drug Enforcement Agency (SCDEA) which deals with drugs and organised crime. That role has proved particularly contentious and concerns that the SPSA was interfering with the agency's autonomy triggered the early retirement of the SCDEA's founding director last November.

The chief constable of Strathclyde, Stephen House, has argued that the SPSA should be made more accountable, possibly to a board. Accountability is a key issue. Each police force is under the control of a board whose members are drawn from the local authorities in their area. The SPSA, as a non-departmental body, is instead answerable to civil servants and ultimately to ministers. The authority's chief executive wants its remit to be extended further and has been backed by HM Chief Inspector of Constabulary. There may be efficiency arguments in their favour (although theoretical efficiency is not always easily translated into practice), but it is clear that the tension between the chief constables and the chief executive of the SPSA and senior civil servants is now close to civil war.

This situation cannot continue.

The increasingly bitter arguments over how Scotland should be policed have become corrosive rather than constructive. It may be that amalgamating forces or some of their services (as in the new unit) is the way forward, but that should not be decided by a pact among chief constables. It is up to the Justice Secretary to establish a strategy for policing Scotland that is effective and accountable but, above all, allows senior officers to get on with preventing and solving crime. It is time he did so.