It is clearly expecting too much of Westminster that, when a recently retired cabinet minister calls for mature debate on drugs policy, a mature debate might actually follow.

Bob Ainsworth was hardly a high-profile figure in the Labour government, but he has served in the Home Office and the Ministry of Defence, from which perspective he concluded that the "war on drugs", as currently organised, is unwinnable. Safely out of office, he last week expressed the politically delicate but entirely sensible proposition that the current consensus around drugs prohibition is flawed and that it is time other measures were considered. Those might include decriminalisation of less harmful substances and allowing doctors to provide addicts with legal, clean supplies of drugs such as heroin that, when bought on the streets, are more toxic and fuel crime.

It is only a pity no politician can find the courage to raise the same questions while actually serving in government.

The Observer has called for just such a debate in the past. That is not to deny the harm that drugs do. Quite the contrary. It is because Britain's drug problems are so pernicious and costly that an evidence-based quest for solutions is so badly needed. And the evidence is that the current approach has failed.

The goal is to stop people taking drugs and to punish those who profit from the trade. The outcome is a flourishing market in which anyone can get hold of a banned substance at any time of day and to the enormous financial advantage of vast criminal organisations. An additional feature of the current regime is that ordinary users are recruited into crime, steered away from mainstream society and into prison where their chances of rehabilitation diminish.

Meanwhile, this whole edifice requires that the UK advocate at international level a policy of forcing governments in opium and coca-producing areas into futile military confrontation with drug exporters. These dirty civil wars, raging across Latin America, west Africa, south-east and central Asia have had no measurable impact on consumption in the west but have cost millions of innocent lives. The UK's own military endeavours against the Taliban in Afghanistan are intertwined with that country's status as a narco-state. Throughout the war, it has continued to provide, scarcely disrupted, the vast majority of heroin used on British streets.

What lower depth of abject failure must a policy plumb before it comes up for review?

The current government has no strategy to curb drug use other than more of the same on a tighter budget.

Mr Ainsworth is clearly not alone in craving a rational debate; that appetite is felt across the political spectrum. Amid much recrimination, one of few supporting voices came from Peter Lilley, a Conservative cabinet minister under Margaret Thatcher and John Major. But party leaders still fear engagement with reforming ideas for fear that their opponents will resort to populist jibes about "softness". This stalemate is crippling policy innovation.

Some overtures must be made between the main parties so that a truce can be declared. Failure of the current approach might then be publicly acknowledged and non-partisan work towards a different solution begun.