A mother of a seven-year-old epileptic boy receiving medicinal cannabis oil treatment has launched a fresh campaign after new guidelines restricted the use of the product.
The law on the use of medicinal cannabis changed this month and Hannah Deacon hoped it would make products like cannabis oil more accessible.
But the new rules do not recommend the use of cannabis oil at all.
NHS England has been approached for comment.
Ms Deacon, the mother of Alfie Dingley, from Kenilworth, petitioned the government in March after she found his condition improved when he was given a cannabis-based medication in the Netherlands, where it is legal, in September 2017.
Although she has secured continuing prescriptions for Alfie, she said the new rules were a "real blow" for families in similar situations and has launched a petition to encourage doctors to "prescribe full extract oil without fear".
The petition has amassed more than 360,000 signatures in less than a week.
The bodies that issued the guidance said cannabis oil is not recommended because there was "no quality evidence" of it being used safely and effectively for pain relief.
The new guidance, issued by the Royal College of Physicians (RCP) and The British Paediatric Neurology Association, also specified doctors prescribing any treatment involving medicinal cannabis must be specialists.
NHS England agreed to continue to issue Alfie's cannabis oil prescriptions provided they came via expert Prof Mike Barnes.
"I feel incredibly guilty that it's only through our campaign that we have been able to secure this for Alfie when there are so many others who will find they are unable to get the treatment because of the guidance," Ms Deacon said.
Formal guidelines on prescribing medicinal cannabis are expected to be published by the National Institute of Health and Care Excellence (NICE) in October 2019 and the RCP guidance remains under review until then, an RCP spokesman said.