Alcohol 'more harmful than heroin' says Prof David Nutt:
The report is co-authored by Professor David Nutt, the former UK chief drugs adviser who was sacked by the government in October 2009.
It ranks 20 drugs on 16 measures of harm to users and to wider society.
Members of the group, joined by two other experts, scored each drug for harms including mental and physical damage, addiction, crime and costs to the economy and communities.
The BBC's home editor, Mark Easton, writes in his blog that the study involved 16 criteria, including a drug's affects on users' physical and mental health, social harms including crime, "family adversities" and environmental damage, economic costs and "international damage".
The findings run contrary to the government's long-established drug classification system, but the paper's authors argue that their system - based on the consensus of experts - provides an accurate assessment of harm for policy makers.
