A CANNABIS crackdown is looming, as proposed changes to the law reducing the amount a user can carry without facing criminal charges gain support in Parliament.

Opposition substance abuse spokesman Duncan McFetridge revived a plan to reduce the amount of cannabis for which a person receives only a fine - and is not charged - from 100g to less than 25g. Carrying more than 25g would become a criminal offence.

The proposed changes, originally introduced by independent MLC Ann Bressington, would also result in the fine for possession of less than 25g being increased to from $150 to $300.

Ms Bressington, when explaining her plan in 2010, said current laws allowed a dealer to be in possession of 100g, or up to 50 two-gram bags with a potential value of more than $1000, without the risk of criminal conviction. or a fine of more than $300.

Family First MLC Dennis Hood has also laid out his own plans to toughen penalties for growing marijuana plants.

He wants the approach of simply fining people for growing one plant removed and to increase the maximum penalties for growing up to five plants from $1000 to $2000 and up to 19 plants from $2000 to $10,000.

Dr McFetridge said if the changes to possession laws could not be agreed to next week, the final sitting week before the election, the Liberal Party would restore it after the election.

"If we are in government it will be something we bring in very quickly," he said.

"We feel that the control of marijuana ... is something we need to continually emphasise and to amend legislation should we find that the current legislation is out of step with the best recommendations from the police, health professionals and other members of the public.

" ... we are protecting people who may quite innocently think that smoking marijuana and consuming marijuana is not a big deal. Well, it certainly is."

A government spokesman said it was considering a position on all of the proposed changes, but pointed out that the Liberals last week did not vote to support the passage of laws that would strip drug traffickers of their assets.

The vote was delayed for six months with the support of the crossbenchers.

Mr Hood said in parliament that the purpose of the criminal law was to act as a deterrent to criminal behaviour, not an encouragement to commit a crime, and that the money a dealer stood to make was far greater than the penalties.

"If deterrence is completely lacking, the criminal law is simply not performing its function," he said.