MAXIMUM fines for possessing small amounts of cannabis will increase more than 10 times when new WA drug laws come into force on August 1.

After 2 1/2 years of promising to get tough on marijuana users, dealers and growers, the Liberal-National Government's "war on drugs" is about to begin.

The penalty for possessing less than 30g of cannabis will jump from a $100 fine to a maximum of $2000 and the possibility of two years in jail.

The penalty for growing up to two marijuana plants is a $200 fine, but that will jump to a maximum $2000 fine and prosecution with the prospect of two years behind bars for growing any number of plants.

And the penalty for businesses caught selling smoking implements to children will increase from $25,000 to a possible $120,000 and two years jail.

"We are declaring war on drugs and this is just the beginning," Police Minister Rob Johnson told The Sunday Times yesterday.

As well as beefed-up fines, anyone found with more than 10g of the drug will be charged with drug possession and face court. If found guilty, they will get a criminal record. Presently, anyone caught with 30g or less receives a small fine and no record.

Other changes include:

* People caught with 10g or less will have to attend mandatory education sessions.

* The sale of smoking implements to adults will also be outlawed, with fines of up to $50,000. At the moment it is an offence only to sell smoking paraphernalia to children.

Mr Johnson admitted the laws had been a long time coming, but said they were vital for WA.

"Just ask any parent whose son or daughter's use of cannabis led to an addiction to harder drugs or caused serious health or mental health problems such as schizophrenia," he said.

"They will tell you that illicit drugs have ripped their family apart and ruined many lives. We owe it to our children to do everything we can to protect their future, which is why this Government makes no apologies for its tough approach on drugs."

But drug experts yesterday cast doubt on whether the laws were sensible.

Steve Allsop, director of the National Drug Research Institute, said cannabis use had declined after the introduction of the laws by Labor in 2003.

"There is no evidence it (Labor's cannabis policy) encouraged use," he said.

He also questioned whether police could enforce the laws.

"Tougher penalties are not likely to have an impact because only about 3 per cent of people who use cannabis are detected by police," Prof Allsop said.

"Directing them all to treatment might not be the best use of limited resources and may limit access to treatment for those who voluntarily seek help.

"Getting a criminal record can have disastrous implications, reducing job options and so on.

"Some might say fine, they broke the law. But a criminal record can marginalise a person, increasing, not decreasing, risks and harm for all of us."

Police Commissioner Karl O'Callaghan said he welcomed "any law reforms that will help combat the scourge of this insidious criminal industry in WA".

Under the new laws, the only reprieve for offenders convicted of minor cannabis possession offences is that they will be able to apply to have a conviction spent after three years, provided they are not convicted for further offences in that period.

"I am particularly heartened by the decision that gives people convicted of minor cannabis possession offences (the right) to apply for a spent conviction after three years, which gives them a much better second chance at turning their lives around than the current 10-year wait to earn a spent conviction," Mr O'Callaghan said.