A regime where currently illicit drugs are regulated and legalized would provide numerous benefits to Britain, not the least of which would be up to $20 billion a year in savings to government, crime victims, and drug users, according to a comprehensive comparison of the costs of drug prohibition and drug legalization.

The figure comes from A Comparison of the Cost-effectiveness of Prohibition and Regulation, a report released Wednesday by the British drug reform group the Transform Drug Policy Foundation. The group says it is the first time anyone in Britain has attempted an across-the-board comparison of the differing approaches to drug use and sales.

According to official British policy, policies or programs should be assessed by a cost-benefit analysis or impact assessment, but that has never been done with drug prohibition. Instead of evidence-based policies, the British government has relied on mere assertion to justify maintaining prohibition and to argue that the harms of legalization would outweigh its benefits.

Now, Transform is calling the government's bluff. According to its analysis, which examined criminal justice, drug treatment, crime, and other social costs, a regime of regulated legalization would accrue large savings over the current prohibitionist policy.

Transform postulated four different legalization scenarios based on drug use levels declining by half, staying the same, increasing by half, and doubling. Even under the worst case scenario, with drug use doubling under legalization, Britain would still see annual savings of $6.7 billion. Under the best case scenario, the savings would approach $20 billion annually.

"The conclusion is that regulating the drugs market is a dramatically more cost-effective policy than prohibition and that moving from prohibition to regulated drugs markets in England and Wales would provide a net saving to taxpayers, victims of crime, communities, the criminal justice system and drug users," Transform found.