Mr Palmer, who spoke at the recent Australian Medicinal Cannabis Symposium in Tamworth, called for a radical overhaul of authorities’ “tough on drugs” mantra. 

He said the prohibition approach was “badly broken”, claiming it made criminals of casual users without “scratching the surface” of large-scale drug supply rings.

“Despite all the arrests and all the seizures, we’ve hardly made a difference in supply or price,” Mr Palmer said.

“I’m not saying we should stop doing it but we must be focused on the illicit drug enterprises.

“By treating use and possession in a criminal way, we are making criminals of young people for what is essentially a social behaviour.”

He said that, as a barrister, he represented many young people whose futures were irrevocably altered for a minor drug possession conviction.

“They had applied to be police officers, join the defence forces or for a visa overseas,” Mr Palmer said.

“Their future was put in jeopardy for half a matchbox full of cannabis.

“It’s just nonsensical to me. 

“Young people have always experimented; they’ve done that throughout history.”

He said drug use should be treated as a health, not a criminal, issue.

Mr Palmer was the AFP commissioner from 1994 to 2001 and was responsible for overseeing some of the largest drug busts in Australian history.

He said there was “overwhelming” evidence medical marijuana should be legalised, saying it had fewer side effects and more benefits than many pharmaceutical drugs.

Meeting Tamworth’s Haslam family and witnessing the courage of Oxley police commander Clint Pheeney, who publicly vowed not to prosecute the Haslams for possession, convinced him to enter the medical marijuana debate, he said.

His comments come the day after a cross-party bill was tabled in the federal Senate that would pave the way for states to legalise medical cannabis.