Patients are being denied NHS prescriptions for medicinal cannabis despite it now being legal, according to campaigners.

Carly Barton claims her experience so far of trying to get the treatment on the NHS since the law change feels "like being blacklisted".

Unable to afford to pay for another costly private prescription, she says if policy does not change soon it will force her and other patients to "break the law" again to get medication on the black market.

The former fine art lecturer is believed to be the first patient in the UK to have been prescribed the unlicensed drug by a private doctor, costing £2,500 for treatment lasting three months.

After a stroke in her early twenties she developed fibromyalgia - a condition causing constant pain. She says other approved strong opioid medication, including morphine and fentanyl, does not work and leaves her feeling "zombied".

The 32-year-old is unable to afford more private treatment so has tried to get an NHS prescription, but found her referral to a specialist hospital doctor in Brighton was rejected.

She went to the Royal Sussex County Hospital on Wednesday for an appointment which she said was confirmed by letter. On arrival she discovered it had not been booked and was told to seek treatment elsewhere.

Ms Barton, who lives in the East Sussex city, said: "It's like being blacklisted.

"They won't even let me in the door to discuss it.

"I spoke to a staff member who looked at my record and told me I would have to go to another county for treatment. I will try to get a referral somewhere in London now.

"It took me months to get this first appointment. I'll probably have to wait another six months.

"I'm going to have to break the law again."

The Government announced plans to reschedule the drug earlier this year and doctors have been able to prescribe cannabis products to patients in the UK since November 1.

It came after the high-profile cases of young epilepsy sufferers Alfie Dingley and Billy Caldwell, whose conditions appeared to be helped by cannabis oil.

Only specialist doctors can provide the treatment, and only when all other options have been exhausted.

Brighton and Sussex University Hospitals NHS Trust said it refused the referral - made by Ms Barton's GP in August for a medication review to discuss an NHS prescription for medicinal cannabis - because the law had not yet changed when it was received. The letter confirming an appointment was an "administrative error", it added.

A trust spokeswoman said it does not "blacklist" patients and takes exception to the accusation. But she confirmed any fresh referral would still be rejected because it is not a service the trust is "currently able to provide" and it is awaiting NHS guidance on which organisations will be able to offer this treatment.

But an NHS England spokeswoman said: "If a trust has specialist doctors there should be no reason why it [medicinal cannabis] cannot be prescribed."

She said if trust bosses state it cannot provide the service they will be "inflicting those rules upon themselves".

The spokeswoman stressed the treatment was "rare" and only used in exceptional circumstances.

Ms Barton, a deputy director of patient advocacy group United Patients Alliance, claimed many others are also still struggling to get treatment.

She said: "The guidelines do not work and need to change."

The incident follows a complaint Ms Barton has made to Boots after claiming she was "laughed out of the pharmacy" by a staff member when she tried to collect her private prescription at its main Brighton branch.

The retailer did not respond when contacted for a comment but in an email to Ms Barton said it was investigating her claims.