Patients in New South Wales will be able to access medicinal cannabis within days of a doctor prescribing it, in what the federal Health Minister says sets a national benchmark.

Health Minister Greg Hunt said the State and Federal Governments had "taken a machete" to red tape in order to provide "direct and immediate access" to medicinal cannabis.

Instead of both the Commonwealth and NSW Health overseeing the approvals, NSW will rely on a single clinical assessment by the Therapeutic Goods Administration (TGA).

Current regulations mean the approval process through the states and the TGA can take months.

Mr Hunt said the changes would come into effect in the coming weeks.

"Where the doctors say it is required, we'll make sure it is available in a matter of days," he said.

"New South Wales is now the national leader — we have had tremendous discussions with Tasmania and Victoria, and so I am hopeful that will make progress with them very shortly — but the benchmark has been set here and this is about saving lives and protecting lives, it's about giving people the capacity to go through their treatments."

The current approval process can take months. ( Supplied: Roll on Ben Oakley Facebook )

NSW Minister for Health and Medical Research Brad Hazzard said the change would make a huge difference to patients.

"When people have got that diagnosis of cancer and they are having the treatment, they are having the chemo, they obviously often feel very sick, nauseous, vomiting," Mr Hazzard said.

"This will allow a very fast response to allow them to get access to what can be … certainly a medicine that can assist you with the nausea and the vomiting.

"It also can assist children who suffer fits from a range of illnesses."

Doctors seek advice on when to prescribe

But Mr Hazzard foreshadowed challenges in convincing medical practitioners that they could prescribe the drug in certain circumstances.

"For that reason NSW has a $6 million advisory service that we established just a few months ago, and what that enables doctors to do is make a phone call and find out how can medicinal cannabis possibly assist your patient," he said.

"There are many negatives if not managed appropriately."

The Medical Cannabis Council welcomed the move to harmonise the prescription approval processes, but cautioned access to medical cannabis for patients in NSW was still not guaranteed.

The industry group said many doctors treated medicinal cannabis as a "medication of last resort".