Doctors in Scotland yesterday voted in favour of cannabis drugs being prescribed on the NHS to ease the suffering of patients.

Members of the British Medical Association, meeting in Dundee, backed a call for change in the law to allow the use of cannabinoid medication to treat disease.

Dr Andrew Thomson, a Scottish GP and leading figure in the BMA, told the association's Junior Members Forum he had watched one of his patients suffer intolerable pain from multiple sclerosis and was powerless to suggest she took cannabis for her relief because of the law.

"A lot of our patients turn to using cannabis to try to relieve their pain - let's not make them criminals," he said. "Let's not turn pain into punishment."

His patient, who has now died, was a professional woman who knew the anecdotal evidence about cannabis relieving pain. However, Dr Thomson explained that she had been a law-abiding citizen all her life and could not contemplate committing a criminal act.

He told The Herald: "She knew it would be good for her, but her morals would not allow her to break the law so she suffered and suffered and suffered.

"It was frustrating to see it but I could not encourage her to use it. I know what is best for my patient potentially but I am not allowed by the system to use what would relieve the suffering."

There is scientific evidence to suggest that cannabis may be useful for alleviating a range of conditions, including the side effects of chemotherapy, and trials of treatments that use cannabis derivatives have taken place. However, cannabis continues to cause concern as a street drug and this week a report is expected to warn that use has increased rapidly among young people despite high profile anti-drugs campaigns.

The BMA Junior Members Forum called for the BMA to lobby the government to make the necessary legal changes to allow the cannabinoid part of the cannabis plant, the active ingredients, to be researched and developed as a treatment.

The forum, which brought together junior doctors from across the UK over two days, also demanded a halt to any further private finance initiatives in the health service.