The South Australian Government has backed down on a key part of its push to crack down on illegal cannabis use, and will no longer push for jail terms for cannabis possession.

At the election, the Liberals promised to launch a "war on drugs" and Vickie Chapman — now Attorney-General — promised to bring penalties for cannabis in line with other drugs like ecstasy and heroin.

That meant maximum prison terms of two years, and a quadrupling of fines from $500 to $2,000.

Cannabis possession was decriminalised in South Australia in 1987, and the most common penalty for possessing less than 25 grams is a $125 fine.

Attorney-General Vickie Chapman said the decision was made after considering the public response, and the opposition from within parliament.

She said it was important to make sure other elements of the bill were not delayed or blocked.

"We didn't get 100 per cent — we got 90 per cent, we're happy with that," Ms Chapman said.

"The Cabinet has confirmed that they're supporting that because it's just so important.

"We've got reforms in relation to obviously commercial manufacture. We've also got important reforms on penalties, including personal use."

While the Government is backing down on prison terms, it will still push ahead with other measures in the bill, including increasing fines and only allowing offenders to go to the drug diversion program twice in a four-year period.

An ABC Adelaide social media poll on 'What should South Australia do to regulate cannabis use?' had more than 18,000 people voting in favour of decriminalisation and 723 people voting in favour of stronger penalties.

Bill would not have passed parliament as it was

The Government's move to increase prison terms faced opposition from Labor and the Greens, along with legal and medical circles.

The Law Society said the changes would clog up an already busy justice system, while health experts questioned whether the penalties would decrease use.

Deputy Opposition leader Susan Close said Labor did not support putting people in prison for possession of cannabis.

"The community does not want to see our jails full of people simply for possessing cannabis," Dr Close said.

"We would need to go after the big guys in organised crime and not fill jails up with young people who have tried a joint."

Likewise, Greens MLC Tammy Franks said she was glad the Liberals had "backed away from that stupid policy".

She said it was the biggest "over-reach" in the bill but not the only one.

"Quadrupling fines for personal use also has no evidence base to it other than revenue raising," Ms Franks said.

"We'll be testing that in the Upper House."

Increasing fines for cannabis possession was a recommendation of deputy coroner Anthony Schapel in his 2017 findings into the murder of 18-year-old Lewis McPherson by Liam Humbles in 2012.

Police issued Humbles with a drug diversion notice because he said cannabis in his possession was for personal use.