London, Nov. 1 (Reuters): Alcohol is a more dangerous drug than both crack and heroin when the combined harms to the user and to others are assessed, British scientists said today.

Presenting a new scale of drug harm that rates the damage to users themselves and to wider society, the scientists rated alcohol the most harmful overall and almost three times as harmful as cocaine or tobacco.

According to the scale, devised by a group of scientists including Britain’s Independent Scientific Committee on Drugs (ISCD) and an expert adviser to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA), heroin and crack cocaine rank as the second and third most harmful drugs.

Ecstasy is only an eighth as harmful as alcohol, according to the scientists' analysis.

Prof. David Nutt, chairman of the ISCD, whose work was published in the Lancet medical journal, said the findings showed that “aggressively targeting alcohol harms is a valid and necessary public health strategy”.

He said they also showed that current drug classification systems had little relation to the evidence of harm.

Alcohol and tobacco are legal for adults in Britain and many other countries, while drugs such as ecstasy and cannabis and LSD are often illegal and carry the threat of prison sentences.

“It is intriguing to note that the two legal drugs assessed — alcohol and tobacco — score in the upper segment of the ranking scale, indicating that legal drugs cause at least as much harm as do illegal substances,” Nutt, who was formerly head of the influential British Advisory Council on the Misuse of Drugs (ACMD), said in a statement about the study.

Nutt was forced to quit the ACMD a year ago after publicly criticising ministers for ignoring scientific advice suggesting cannabis was less harmful than alcohol.

The WHO estimates that risks linked to alcohol cause 2.5 million deaths a year from heart and liver disease.