Fewer than five NHS patients have received medical cannabis since its legalization.
The government states that more research is needed before routine NHS prescriptions are allowed.
Hannah Deacon, whose son uses medical cannabis, says families are left with no choice but to break the law as doctors often refuse to prescribe it due to bureaucracy.
Deacon, co-founder of the Medcan Family Foundation, marched with others to lobby for change, urging the government to clarify the pathway for prescriptions.
Cannabis-based medicines currently available on the NHS include Sativex for multiple sclerosis and Epidyolex for certain epilepsy types.
GPs can prescribe cannabis-based products under specialist doctor guidance in shared care agreements, with exceptions possible through individual funding requests.
The government emphasizes an evidence-based approach and calls for more research before wider NHS access.
Families report paying up to £2,000 per month for private prescriptions due to limited NHS access.
Deacon estimates that hundreds, if not thousands, are turning to illegal cannabis and calls for it to be treated differently from other medicines.