It was the day Michael Lambert watched his infant daughter suffer a violent two-and-a-half-hour seizure that he says he decided breaking the law was a small price to pay for her life.

Katelyn had been diagnosed with a severe form of epilepsy known as Dravet Syndrome and her family was told there was a one-in-six chance she would be dead before she turned 18.

"They told me, 'Go out and have as much fun as you can with this child now, just forget she's got epilepsy, because you don't know how long you'll have with her'," Mr Lambert said.

At just 11 months old, Katelyn could have seizures every 15-20 seconds and for hours on end.

Now seven, she averages one a year.

Her father said he believed this was because he had been giving her five drops of illegal cannabis oil every day for nearly five years.

Katelyn's paediatrician and neurologist admitted she had shown dramatic improvements.

"Before then I thought I'd be arrested but all of a sudden I thought, 'Damn it, I'm watching my daughter die in front of me, I've got to break the law'," Mr Lambert said.

Advocates say system is failing

Katelyn has been taking a cocktail of drugs for the past four years, including traditional opioids and cannabis oil. ( ABC Central Coast: Meghna Bali )

Earlier this week, the ABC revealed more than 3,000 medicinal cannabis scripts had been approved by the Therapeutic Goods Administration (TGA) from March 2018 to January 2019.

But conservative estimates suggested up to 100,000 Australians were still using it illegally to self-medicate.

Advocates said this was an indication the system was failing.

The Federal Government announced a streamlined application process for medicinal cannabis last year, which would allow approved patients to get access to the drug in 48 hours.

But Mr Lambert disputed claims the process had been made easier.

"Everybody knows from the Health Minister to the Prime Minister, I wrote to them all, I begged for help," he said.

"They told me, 'We're going to come up with a solution, just hang in tight', but I'm worried that the next package is not going to arrive, that my daughter's going to get electrocuted to death in front of me, because she's missing the most vital ingredient in her medicines."

Michael Lambert says it took him two months to obtain MediCabilis through the Special Access Scheme. ( ABC Central Coast: Meghna Bali )

In theory, a patient like Katelyn had several options to obtain medicinal cannabis.

The first was to get on a clinical trial.

One underway in New South Wales is investigating the impact of cannabis on children with severe treatment-resistant epilepsy.

But limited spots meant only about 100 children had access to it, and Katelyn was not on the list.

Another option was to find a doctor who was an Authorised Prescriber (AP) of a specific cannabis medicine.

To become an AP, however, a medical practitioner must complete a rigorous application process, get approval from the Therapeutic Goods Association, obtain endorsement from an ethics committee, check for additional state or territory requirements and provide the drug supplier their authorisation.

But privacy laws did not allow people to search for an AP.

The third pathway, under the Special Access Scheme (SAS), allowed practitioners in most states and territories to apply for Commonwealth and state approval in an online application.

However, some found it difficult to find a doctor willing to go through this process.

Mr Lambert estimates buying legal cannabis would cost him more than $53,000 a year compared to $2,700 on the black market. ( ABC Central Coast: Meghna Bali )

Dr Sanjay Nijhawan from Cannabis Access Clinics said a lack of awareness had discouraged doctors from engaging with it.

"We have not educated our GPs, the medical schools don't know enough about it … at the moment it's pretty raw, it's early days," he said.

Katelyn's current dose of MediCabilis had been obtained through the SAS and did not come cheap.

Mr Lambert said a bottle that would last his daughter four days cost $585.

"The minimum dose recommended on the bottle is $140 a day and I can get it [for] $7.50 a day on the black market," he said.

"I've got three choices — don't give it to her and injure her, keep breaking the law or what extra job am I going to get to pay for it?"

Rhys Cohen from Sydney University's Lambert Institute for Cannabinoid Therapeutics said high costs were driven by a lack of transparency around the supply chain for these products.

"There might be a cultivator overseas, a manufacturer, an international distributor, a local distributor and a pharmacy … all taking their cut," he said.

"I think it's fair to say Australians are getting gouged by some opportunists."

'Between a rock and a hard place'

Katelyn could be hospitalised for days after an extended seizure. ( Supplied: Michael Lambert )

Carol Ireland from Epilepsy Action Australia said she had seen a change in attitude toward cannabis as a viable treatment in the past five years.

She conceded the system had left parents like Mr Lambert with minimal options.

"They're not hippies, they're not people who are living alternative lifestyles and they're not people who want to break the law — they're families between a rock and a hard place," she said.

Mr Lambert paid for his actions when he was found guilty in 2017 of possession and cultivation of cannabis, but said he had no regrets.

"She has catastrophic epilepsy, the side effect is she gets her life back, she doesn't get brain damage, she can live, she can breathe, and they can't stop it but I can with a little bit of hemp," he said.

A 2017 review from the National Drug and Alcohol Research Centre found that the strongest evidence for medicinal cannabis was in children and young adults with drug-resistant epilepsy, for which CBD products had been shown to reduce the frequency of seizures by 50 per cent or more in up to half of paediatric patients.

The review also found there was limited evidence about the effectiveness of medicinal cannabis for use in different medical conditions, and little was known about the most suitable doses of individual cannabis products.

Professor Jennifer Martin, director of the Australian Centre for Cannabinoid Clinical and Research Excellence, said when it came to the scientific evidence behind medicinal cannabis, the picture was mixed.

"The evidence of non-cancer pain is actually not that strong. There was a big review in the US a few years ago, which suggested there would be some benefit for some patients," she said.

She said it was better for patients to use drugs that had been registered by the TGA first, before trialling medicinal cannabis.

Professor Martin said the scientific evidence of benefits was stronger for treating conditions such as kids with epilepsy who had not responded to medication.

Calls for independent regulator

Lucy Haslam, who has been spearheading the movement for access to medicinal cannabis since 2013, said she was "bitterly disappointed" by the state of the current laws.

Her son Dan was a fierce advocate for the medicine and died aged 25, a year before Australia's laws were passed.

"I used to be proud of what we'd done but nothing much has changed for patients," she said.

"We find that the Government's trying to put a lot of spin on it and claim it's been victorious, but it's been a disaster."

She has joined Greens leader Richard Di Natale in calling for the establishment of a national regulator.

"Every other country with a sophisticated cannabis program has elected to set about doing it through an independent regulator. That's what we should've done," she said.

The now defunct Greens Bill was introduced to parliament in 2014 and would have allowed for the creation of a single body in charge of approving, licensing, importing and exporting medicinal cannabis.

The Federal and New South Wales Health Ministers both declined to comment.