Greens Leader Richard Di Natale says approval for farmers to grow medicinal cannabis does little to get the drug into patients' hands.
Senator Di Natale says there is a "bottle neck" between growth and patient supply and the legislation announcement by the government does nothing to address access the drug.
"We've addressed the issue of supply by licencing growers but we've ignored the much bigger problem which is approving the drugs for use so that doctors can prescribe it," Senator Di Natale told reporters on Saturday.
"I fear these changes won't allow that to happen."
Health Minister Sussan Ley said on Saturday the government was finalising draft amendments to the Narcotics Drugs Act 1967 to allow growth of cannabis for medicinal and scientific purposes.
Ms Ley said the changes will deliver a safe, legal and sustainable supply of locally produced product for the first time.
