CANNABIS would be sold legally in post offices in packets that warn against its effects under a proposal outlined by the head of a Sydney drug and alcohol clinic.

The director of the alcohol and drug service at St Vincent's Hospital, Alex Wodak, said Australia needed to learn from the tobacco industry and the US Prohibition era in coming to terms with his belief that cannabis use would replace cigarette consumption over the next decade. "The general principal is that it's not sustainable that we continue to give criminals and corrupt police a monopoly to sell a drug that is soon going to be consumed by more people than tobacco," he said.

"I don't want to see that [industry] fall into the hands of tobacco companies or rapacious businessmen.