Mary Brett, of Cannabis, Skunk, Sense, which aims to prevent the use of drugs, says the report authors "haven't thought it out".
"Drugs are illegal because they are dangerous. Cannabis is getting stronger each year.
"People haven't grasped how cannabis affects the brain. It contains chemicals within the plant that stick in the brain cells. This impairs the transmission of all the other chemicals that carry out functions in the brain."
According to the commission, the government's efforts to ban drugs have not reduced their availability and may have even done more damage. So rather than trying to prevent their use entirely, ministers should focus on limiting the damage.
The report states: "Just like with gambling or eating junk food, there are some moderately selfish or risky behaviours that free societies accept will occur and seek to limit to the least damaging manifestations, rather than to prevent entirely.
"Seeing all drug use as invariably problematic can reduce the cost-effectiveness of policy.
"Taking drugs does not always cause problems, but this is rarely acknowledged by policy makers.
"We do not believe that pursuing the goal of encouraging responsible behaviour requires the prevention of all drug use in every circumstance."
Controversially, it also recommends changing the law to allow people to grow small amounts of cannabis in their homes. This would help undermine the mass production of the drug illegally.
Professor Colin Blakemore, who helped write the report, said: "The overwhelming consensus now is that it is unethical, inefficient and dangerous to use untested and unvalidated methods of treatment and prevention. It is time that policy on illicit drug use starts taking evidence seriously as well."
The commission is an independent charity set up in 2007 to analyse drug policy in the UK. It's not government funded and claims not to have any particular standpoint.
This is the final report from the charity, which will shut-down in December.
Although drug use in Britain has fallen in recent years, it is still higher than most other countries. About one in ten adults has taken an illegal substance in the past year compared to a global average of one in 20, the report states.
- DAILY MAIL