The federal government is open to legalising the medicinal use of marijuana, two prominent Liberals say.
Senator Ian Macdonald and MP Warren Entsch are supporting a private cross-party bill due to be tabled in parliament later on Thursday.
Mr Entsch says Prime Minister Tony Abbott and others in the government support medicinal marijuana while Senator Macdonald doesn't expect the issue will need to go to a conscience vote.
"I've actually spoken to the prime minister on this... and he confirmed to me that he certainly supports medicinal cannabis," Mr Entsch told reporters in Canberra.
In August Mr Abbott threw his support behind medicinal marijuana in a letter to radio talk-back host Alan Jones.
"I have no problem with the medical use of cannabis, just as I have no problem with the medical use of opiates," he wrote.
State governments in NSW, Victoria and Western Australia have expressed interest in being part of an opt-in-opt-out system.
Greens health spokesman Richard Di Natale says a regulatory body would determine for what conditions marijuana products could be prescribed.
But a doctor's discretion would still play a big part.
"Some doctors may decide they don't want to be involved in it," Senator Di Natale said.
"The great majority will recognise the immense therapeutic benefit."
The bill also creates a tightly-controlled farming regime for marijuana, similar to medicinal opiates in Tasmania.
Among the other parliamentarians who have thrown their weight behind the bill are Liberal Democrat David Leyonhjelm and Labor's Anne Urquhart.
