Chief Constable Mike Barton of Durham Police has called for the decriminalisation of class A drugs, saying heroin and cocaine should be made available on the NHS.
Barton, one of Britain's most senior policemen, believes that the prohibition of class A drugs has put billions of pounds into the pockets of criminal gangs and that legalising drugs would destroy their power base.
There are 43 known organised crime groups in the Durham Constabulary area alone.
The chief constable, who is the intelligence lead for the Association of Chief Police Officers, says that efforts to reduce illegal drugs had "completely failed".
"If an addict were able to access drugs via the NHS or something similar, then they would not have to go out and buy illegal drugs," he told the Observer.
"Buying or being treated with, say, diamorphine is cheap. It's cheap to produce it therapeutically.
"Addiction to anything is not a good thing, but outright prohibition hands revenue streams to villains."
He suggested that a controlled environment would be a more successful way of tackling the issue.
"Not all crime gangs raise income through selling drugs, but most of them do in my experience. So offering an alternative route of supply to users cuts their income stream off.
"What I am saying is that drugs should be controlled. They should not, of course, be freely available."
Barton compared drugs prohibition to the ban on alcohol in the United States during the 1920s, which created a boom in organised crime.
The officer said drug addicts needed to be treated and cared for, encouraged to break the cycle of addiction - rather than criminalised.
"Since 1971 [the Misuse of Drugs Act] prohibition has put billions into the hands of villains who sell adulterated drugs on the streets.
"If you started to give a heroin addict the drug therapeutically, then we would not have the scourge of hepatitis C and Aids spreading among needle users, for instance. I am calling for a controlled environment, not a free-for-all."
According to a report from the UK Drug Policy Commission, the annual estimated cost to England and Wales of class A drug use is £15bn.
Danny Kuschlick, of campaign group Transform Drug Policy Foundation, said: "We are delighted to see a serving chief constable who is willing to stand up and tell the truth - prohibition doesn't work."