Suggestions that the drug laws need changing, that the global war on drugs has failed, are invariably put down to woolly, liberal, or maverick, thinking. What will be the response then when the suggestions come from a former deputy head of MI6 in a study published by such an established and venerable thinktank as the International Institute for Strategic Studies?

"Drugs have been the commodity which more than any other has primed the pump for the massive rise in organised criminality witnessed since the end of the cold war", writes Nigel Inkster, former MI6 director of operations and intelligence, and author, with Virginia Comolli, of Drugs, Insecurity and Failed States published by the IISS this week.

Drugs still account for about 50% of the profits of organised criminal groups even though many of these groups have diversified into other lucrative activities such as people-smuggling, counterfeiting, and cyber crime, they say.

In principle, therefore, collapsing the black market in drugs ought to have a significant beneficial impact on levels of violence and criminality.

The IISS study is the result of a growing realisation that levels of violence fuelled by narcotics are getting worse, and growing pressure from Latin America for a rethink of current laws prohibiting drugs. It quotes a UN report which warned in 2009: "Collusion between insurgents and criminal groups threaten[s] the stability of West Asia, the Andes, and parts of Africa, fuelling the trade in smuggled weapons, the plunder of natural resources and piracy".

While demand for heroin and cocaine appears to be levelling off in the developed world, the authors point out that Russia and Iran now have substantial populations of heroin addicts, possibly as high as three million in Iran.

Amid all the descriptions and comments on the violence, instability, and corruption in Afghanistan, very few mentions drugs. Yet Afghanistan is the source of 85% of the heroin consumed on the streets not only of western Europe, but of Russia and Iran, along with the rest of the world.

Back in 2001, Tony Blair said Britain would take the responsibility for counter narcotics operations in Afghanistan. It came to nothing. British troops were the first to face the consequences of a policy, so unthought through, that made local Afghans even more suspicious of the motives of foreign soldiers than they already were.

In Afghanistan, say the authors of the IISS study, "the heroin trade helps fuel a long-running insurgency which is unlikely to end in 2014 with the drawdown of Nato/Isaf combat forces, whilst simultaneously perpetuating within the Afghan government levels of criminality and corruption which actively promote the conditions for the insurgency to flourish".

While in Afghanistan the income from opium production represents a "social safety net", some of the poor countries of West Africa "have been taken over and comprehensively corrupted by narcotics-trafficking groups, to the point where the latter secure the loyalty of local populations by providing levels of social welfare far beyond the capacity of states to match", says the report.

The developing world has had to pay for the demand in the developed world for substances which, because they are illegal, acquire an inflated market value "with all the incentives this provides for organised criminal groups".

The study is a welcome clarion call, not for a free-for-all, but for a serious debate based on empirical evidence, free from polemics, emotion, and ideology, about how to eliminate the global black market in drugs - away from prohibition towards a regime based on legalisation combined with regulation.