Tough new penalties for possessing and growing cannabis or selling smoking implements come into force in Western Australia on August 1.

Police Minister Rob Johnson announced on Sunday that the "relaxed, soft drug laws" introduced by the previous Labor government would be repealed and replaced by a stricter regime.

"What it will mean is that those people caught with cannabis will not simply get a slap on the wrist," he told reporters.

But the opposition says the new penalties are just "smoke and mirrors" to make out the government is tough on drugs when it's facing pressure over a growth in clandestine drug labs in the suburbs.

Under the new laws, someone caught with more than 10 grams of cannabis, rather than the 30g under the previous law, will face a penalty of $2000 or two years in jail, or both.