Mr O'Sullivan, a former drug squad detective, said his "mind had opened up considerably" over the course of a Senate inquiry on proposals drafted by Greens Senator Richard Di Natale.

Senator Di Natale's bill would create an independent body of experts, the Office of Medicinal Cannabis, which would license commercial growers and determine how cannabis could be prescribed and dispensed.

Mr O'Sullivan said he had been moved by testimony from people who had sourced cannabis illegally in a bid to ease the suffering of loved ones.

In Sydney on Tuesday, Lucy Haslam, the mother of the late medical marijuana campaigner Dan Haslam, criticised the NSW government for moving too slowly to provide sick people with access to the drug.

"We cannot afford to wait for the results of clinical trials," Ms Haslam told the hearing. Her son died in February, five years after being diagnosed with cancer. "Don't dismiss the urgent need of people now."

NSW Premier Mike Baird credited meeting Mr Haslam with changing his view on medical cannabis, which led to his government announcing clinical trials.

Those trials, for childhood sufferers of intractable epilepsy and chemotherapy-related nausea, are being planned and, if successful, could lead to legalisation of cannabis for medical purposes. Paediatric epilepsy patients will first be enrolled in 2016.

Mr O'Sullivan said it was possible that "tens of thousands and possibly hundreds of thousands of just ordinary, everyday Australian mums and dads" were risking prosecution to obtain cannabis for their loved ones. He said because cannabis was illegal they did not have any assurance of the quality of what they were buying, and were forced into contact with criminals to obtain it.

"We've really got to tidy this up and tidy it up quickly," he said. "There's a real big body of evidence that there's something in this.

"This is one of those ones where it seems as though solutions are just as clear as the nose on your face."

However, Mr O'Sullivan said he remained firmly opposed to the use of cannabis for recreational purposes.

Mr O'Sullivan, who worked as a detective for 17 years before entering Parliament, praised Mr Di Natale for his initiative, and other members of the Senate committee for the "collegiate" approach they had taken to the issue.

"We'll be putting some energy into this to make sure it's walked through our respective parties, and as long as we get the detail right, I think we'll get an outcome here," he said.

Mr Di Natale said medical cannabis was "an idea whose time has come", adding he had been encouraged by the support his bill had received from all sides of politics.

Prime Minister Tony Abbott, Agriculture Minister Barnaby Joyce, Liberal MP Sharman Stone and Labor MP Melissa Parke are among the parliamentarians to express support for medical cannabis.

Senator Di Natale said the challenge was to draft the best legislation possible. He hoped parliamentary debate of the bill might start by the middle of the year.

with James Robertson