The South Australian Government wants to dramatically increase penalties for marijuana possession, as it wages what it says is a "war on drugs".

Key points: Proposed laws to quadruple SA cannabis possession fines

Proposed laws to quadruple SA cannabis possession fines Move recommended by deputy coroner was an election promise

Move recommended by deputy coroner was an election promise Lawyers and doctors prefer focus as health issue

The maximum fine for cannabis possession would be quadrupled to $2,000 under laws to be debated in Parliament this week.

A new maximum prison sentence of two years would be introduced — the same as drugs such as ecstasy or heroin.

Attorney-General Vickie Chapman said marijuana needed to be treated the same as other controlled and illegal drugs, rather than like jaywalking.

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

Quadrupling cannabis possession fines was a Liberal election promise as part of a "war on drugs" slogan.

Other measures included allowing drug-sniffing dogs into schools.

"The plan is to review and increase penalties across the board, from using to supplying, and reducing the opportunity to say, 'well, I'll have treatment," Ms Chapman said.

"We're bringing it into parity [with other drugs]."

Drug diversion program too lenient: Attorney-General

Ms Chapman said too many people were taking advantage of a drug diversion program, which they will now only be allowed to go to twice in a four-year period.

"If we give people a chance to have treatment a couple of times, that's fine, but really this a limit on how lenient we can be in giving people a chance to have treatment instead of a penalty," she said.

"…We endorse that that's an opportunity that should be given, but third time around you don't get that opportunity."

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 17-year-old Liam Humbles in 2012.

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

Opposition to changes from lawyers, doctors and the Greens

The Law Society of South Australia said it would prefer drug use to be treated as a health issue rather than a criminal one.

The chair of the society's criminal law committee, Rachael Shaw said the new laws would clog up an already busy and stretched justice system.

"The society does not support at all the idea in particular that we remove or limit the ability of people to access counselling and education through what is now the diversion program, which has been in place for many years and instead put these people in the criminal justice system," Ms Shaw told ABC Radio Adelaide.

Dr David Caldicott, the clinical lead at the Australian National University's Australian Medicinal Cannabis Observatory, questioned whether the laws would decrease use or harm from marijuana.

"We know for a fact introducing harsher penalties does neither of those things," Dr Caldicott said.

"Maybe it's to generate revenue.

"The likeliest scenario for its purpose is to send a message to those who support these policies — it's a form of virtue-signalling."

Rather than a war on drugs, Greens MLC Tammy Franks said the proposed laws were "a war on the homeless, Aboriginal people and the poor" who were least able to afford to defend themselves in court.

"This is a policy that has failed around the world — prohibition does not work when it comes to drugs," Ms Franks said.

"It is a health issue, not a criminal issue."