Two cannabis-based medicines have been recommended for use on the NHS for the first time.
Epidyolex has been approved for two rare types of epilepsy, Lennox-Gastaut and Dravet syndromes, while the spray Sativex has been recommended for muscle spasms in multiple sclerosis (MS).
Charities welcomed the move, but said thousands of other people who could benefit from cannabis-based medicines were left in limbo.
A change in the law in 2018 made it legal for doctors to prescribe medicinal cannabis.
However, many doctors have been reluctant to do so, citing a lack of clear guidance on prescribing and issues over funding for the drugs.
This has led some families to go abroad in search of medicines, with some bringing them into the UK illegally.
The new guidance from the National Institute for Health and Care Excellence (Nice) looked at cannabis-based products for several conditions.
It found a lack of evidence regarding their use in the management of chronic pain and said people with chronic pain should not be prescribed drugs containing THC (delta-9-tetrahydrocannabinol) – the psychoactive ingredient in cannabis.
It also said more research was needed on cannabis-based medicines to treat forms of epilepsy other than Lennox-Gastaut and Dravet.
Around 8,0000 to 9,000 people in the UK suffer Lennox-Gastaut and Dravet syndromes.
Millie Hinton, from the campaign End Our Pain, said the guidelines were “a massive missed opportunity” to prescribe medical cannabis for thousands of people with a range of conditions.
“It is particularly devastating that there is no positive recommendation that the NHS should allow prescribing of whole plant medical cannabis containing both CBD (cannabidiol) and THC in appropriate cases of intractable childhood epilepsy,” she said
“It is this kind of whole plant extract that has been shown to be life-transforming for a significant number of children, including these involved in the high-profile cases of last year which led to medical cannabis being legalised."
She said Nice is wholly focused on evidence from randomised control trials, but medical cannabis is not always suited to these trials.
She added: “This restrictive guidance is condemning many patients to having to pay for life-transforming medicine privately, to go without or to consider accessing illegal and unregulated sources.”
Simon Wigglesworth, deputy chief executive at Epilepsy Action, welcomed the decision to recommend Epidyolex.
However, he said there were many thousands of people with other complex and treatment-resistant epilepsies who could potentially benefit from cannabis-based medicines.
And he said there was a lack of high-quality clinical evidence, particularly around products that contain THC.
He added: “Though this is disappointing, we appreciate that clinical research is vital to ensure that any treatment recommended for use in the NHS is safe and effective.
“We are aware of ongoing efforts to bring forward research into cannabis-based medicines for epilepsy, including those containing THC, at pace.”
Nice also recommended Sativex to treat muscle spasms in MS, a common symptom of the disease.
Genevieve Edwards, director of external affairs at the MS Society, said: “We’ve been campaigning for access to Sativex for years, and it’s brilliant Nice has finally listened.
“These guidelines are an important first step, but don’t go far enough. No cannabis-based treatments have been recommended to treat pain, a common symptom of MS."