Terminally-ill patients waiting months to access medicinal cannabis could have that slashed to just hours after a backflip by crossbench senators.
The Greens have succeeded in scrapping rules which made it harder for dying patients to access medical cannabis after a failed attempt in May.
The changes mean terminally-ill patients will get quicker, easier access to medicinal cannabis, prescribed by a doctor, by allowing access under the Therapeutic Goods Administration category A list.
Access is now available under category B, which the Greens say can take months for approval.
Tuesday's vote came after One Nation and independent Jacqui Lambie backtracked on their original positions, teaming up with Labor and the Greens to defeat the government.
Pauline Hanson claims she initially voted against the move because she was deceived by the government, saying she was falsely assured terminally-ill patients had access to adequate supplies of the drug.
"I was not informed correctly by the government," she told the Senate.
She rejected government claims that axing the rules would allow unsafe, uncontrolled importation of cannabis into Australia.
Health Minister Greg Hunt slammed the change as reckless and irresponsible, saying it will remove protections against unsafe medicinal cannabis that could be diverted for criminal use.
The move was in defiance of advice from the medicines regulator.
"The Therapeutic Goods Administration could not be clearer that it is a potential risk, not just to health, but to lives," Mr Hunt told reporters in Canberra.
"There is already a safe, legal way to access medicinal cannabis in Australia - 133 patients have been prescribed that."
Greens leader Richard Di Natale labelled the government's complaints "utter nonsense".
"What this change does is ... if you've got a terminal illness you can go and see a GP and if the drug is not available here in Australia, they can order it for you and you can source it from other regulated markets," he said.
Opposition health spokeswoman Catherine King said it was a win for dying Australians.
"We now hope the government gets on with the job of implementing a national scheme and stop scaremongering and stigmatising the people who are trying to access medicinal cannabis," she said.
Doctors warn the move will undermine the existing, safe process for the sake of political point-scoring.
"When it comes to medicinal cannabis we need to keep politics needs out of healthcare," Royal Australian College of GPs president Bastian Seidel said.
"This change undermines the reporting and monitoring processes to the detriment of patients and their doctors."