Video report by ITV News Correspondent Daniel Hewitt
Despite medical cannabis now being legal on the NHS, a limited number of prescriptions have been granted since the law change and some parents are having to pay thousands for import licences and private prescriptions.
An NHS England review has blamed the lack of prescriptions on concerns about both the potential harm to mental health and effectiveness of medical cannabis.
It said more clinical trials need to be carried out and a "UK-wide paediatric specialist clinical network" should be created to help “very cautious” doctors, by providing expert advice on complex cases.
The "forward-looking and positive review" was welcomed by the Medical Cannabis Clinicians Society (MCCC), whose executive director Hannah Deacon spoke to ITV News about the issue.
Her eight-year-old son Alfie Dingley, who suffers from severe epilepsy, was the first of a handful of patients in the UK to receive an NHS prescription for medical cannabis, despite rule changes last year allowing doctors to prescribe it.
She praised the review, which she says "makes some good recommendations of how the NHS can improve access" but criticised a report by the National Institute for Health and Care Excellence (Nice) - the body that recommends NHS spending.
It looked at the use of cannabis-based medicine for people undergoing chemotherapy, suffering from chronic pain, spasticity in people with multiple sclerosis and severe treatment-resistant epilepsy.
NICE said: "The committee were unable to make a recommendation about the use of cannabis-based medicines for severe treatment-resistant epilepsy because there was a lack of clear evidence that these treatments provide any benefits."
Dr Paul Chrisp, the director for the centre for guidelines at NICE, told ITV News: "If you were taking medicine, you would want to know how effective it was and if it was going to cause you problems.
"Medicinal cannabis is exactly the same."
Speaking to ITV News, Ms Deacon claimed NICE had shown "no empathy to the families that I work with that are funding private prescriptions because the NHS doctors will not prescribe".
She said: "There is no thought of what is going to happen to those poor children if those families run out of money."
She added: "(Doctors) don't have any education, they don't have any training, they don't understand.
"The government have failed them, the government are failing the families I work with, whose children will become seriously ill if they're not helped urgently and I just think it's a complete mess.
"What I want to see is Matt Hancock stand up, tell us if he's going to accept these guidelines and these recommendations and tell these families and the people suffering in this country what he's going to do."
The NHS report, titled Barriers to accessing cannabis-based products for medicinal use on NHS prescription, was commissioned by Health Secretary Matt Hancock after “heart wrenching” meetings with the parents of ill children.