MPs, peers and former police officers are to back the publication today of the first ever report outlining a "detailed road map" to the legalisation of drugs in Britain.

The report from the drugs policy think-tank Transform, argues that by 2020 most drug users will no longer buy from unregulated dealers but obtain drugs from specialist pharmacists or licensed retailers, with prescription drugs available for those who can prove clinical need.

The report is backed by Labour MPs Paul Flynn and Oona King; the Labour peer and penal reformer Baroness Stern; the former Times editor Simon Jenkins and former police officers.

Transform's director, Danny Kushlick, predicted that drugs would be legalised in the not-too-distant future because prohibition had been a catastrophe of startling proportions: "Crime has doubled and the government estimates crime costs at AUKP16bn a year. The drugs discourse at the party conferences was stuck in the tough-talking rhetoric. However, there is now a groundswell of interest in looking beyond the drug war, to consider alternative policy options that will be more effective."