Medicinal cannabis will be legally grown in Australia, with changes passed to create a national licensing scheme for growers.

The changes to the Narcotic Drugs Act, which passed the Senate on Wednesday, create a national body that can issue licences to growers and regulate local crops of medicinal marijuana.

Lucy Haslam, medical marijuana campaigner Credit:Peter Rae

The drug remains a "prohibited substance" under the poisons schedule. But Health Minister Sussan Ley said the Department of Health and the Therapeutic Goods Administration were "well-advanced" in considering downgrading it to a "controlled substance" class, putting it in the same category as morphine.

"This will in turn reduce any barriers to access, no matter what state a patient lives in," she said.