NSW has moved transformational changes to its road laws, which would allow registered medicinal cannabis users to continue driving with low amounts of THC (tetrahydrocannabinol) in their system.
A three-strike system will also be enforced if a reading is higher, with two warnings issued before a $704 fine and a minimum three-month licence suspension.
But opponents - including roadside assistance and motoring advocacy organisation the NRMA - have pointed to NSW government research around driving behaviour and attitudes after taking drugs.
The 2025 study - conducted by the state's Centre for Road Safety - involved more than 5000 drivers and found 54 per cent of those using prescribed cannabis either took more of the drug than prescribed or used it for recreational purposes.
Four in 10 of those prescribed medicinal cannabis said they also used illicit cannabis.
"Normalising drug driving flies in the face of a rising road toll to which it is now a greater factor than drink driving," NRMA spokesman Peter Khoury said.
"Given the road safety risks of this policy, the government needs to significantly enhance police enforcement."
A Transport for NSW spokeswoman confirmed the research was completed in August 2025 and said it would be released publicly later this year.
"The results will be presented to the Australasian Road Safety Conference in Sydney in October 2026 and are expected to be published on the Transport for NSW website in due course," they told AAP.
State Opposition Leader Kellie Sloane called on the government to reverse course due to the study's findings.
"The government is doggedly pursuing its three-strikes drug driving policy in the face of evidence which it has sat on that will jeopardise the safety of everyone using our roads," Ms Sloane said.
"Labor has ignored the experts who say there is no agreed level of THC which identifies that a driver is impaired, and they've ignored their own study which says medicinal cannabis is being misused."
Roads Minister Jenny Aitchison introduced the laws to parliament on Thursday and insisted the state's roads would remain safe.
"This legislation creates a more common-sense system for patients who use lawfully prescribed medicinal cannabis, ensuring they are treated with dignity and respect," she said in parliament.
The Queensland government announced it would move the other way and significantly strengthen penalties for drug, drink and dangerous drivers.
Queensland Attorney-General Deb Frecklington blasted the NSW reforms.
"We are taking a tough approach," she said.
"If anyone has a medical reason for taking a drug, that is horrific for them they have to do that, but at the end of the day, they shouldn't be driving a motor vehicle."
There are about 300,000 medicinal cannabis users in NSW.
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