A former university lecturer is believed to be the first patient in the UK to be prescribed cannabis by a doctor, following the legalisation of the drug for medical use.

Carly Barton, 32, who used to teach fine art, developed fibromyalgia, which leaves her in constant pain, after a stroke in her early twenties.

For years, she has used cannabis illegally to control her symptoms. But in a UK first, Ms Barton was prescribed medicinal cannabis last month by Dr David McDowell, a private pain specialist.

The government must now authorise a specialist importer to procure the drug from the Netherlands.

The prescription has not been provided on the NHS, and costs £2,500 for a three-month supply.

Cannabis has been legal for medical use since November 1 after a protracted battle to downgrade its legal status.

Campaigners now say that NHS doctors are still constrained by interim guidelines which make it difficult for them to prescribe the drug.

It is understood that some doctors have put up posters telling patients not to ask them for it.

Although Ms Barton has a prescription, a ‘specials’ drug importer must now be given a licence from the Home Office to legally import medical grade cannabis from another country such as the Netherlands. It is thought that it may be weeks before she is given her medication by a pharmacy.

Ms Barton argues that the high cost of her medicine will create a “two tier system”, where most people will not be able to afford cannabis and will have to continue to source the drug illegally.

Speaking to The Telegraph, she said: “It’s momentous that this has happened. It’s the first prescription that was written since cannabis was made illegal since 1928. It’s made history, this bit of paper.

“But the truth of the matter is that he’s given me a three month supply that’s going to cost me £2,500. I’m going to blow all of my savings on this initial prescription, and after this three months is up I’m going to have to go back to being a criminal, breaking the law.”

“There is an unfair system where the rich will have access and the poor will still have their doors kicked in by police.”

She hopes that an NHS doctor will fill out a repeat prescription for the drug when her supply runs out.