A former Home Office minister lent his support to legalising medicinal cannabis amid calls for the government to allow a six-year-old boy to be given the drug to treat his rare form of epilepsy.
Sir Mike Penning backed the move as a new study found cannabis oil may curb the frequency of epileptic seizures.
His support comes as the parents of Alfie Dingley, who suffers 20 to 30 seizures each day, called on the government to let their son use cannabis oil to treat his condition.
The Conservative MP for Hemel Hempstead, urged the Home Office to give Alfie a special licence to use medicinal cannabis in the UK.
His parents launched the End Our Pain campaign after the frequency of Alfie's seizures dramatically reduced when he was treated with cannabis oil during a five-month visit to the Netherlands, where the drug can be legally prescribed.
Sir Mike said: "When I was Police and Justice Minister in the Home Office, I stated clearly in the House of Commons that there needs to be a legalised method of provision for cannabis so that it may be used to treat illnesses like multiple sclerosis and severe epilepsy.
"However, in my view, there is substantial scientific evidence showing that cannabis is a harmful drug and, in its street form, is a gateway drug for many users.
"But surely in the 21st century, we can find an acceptable way to separate the two so that patients who gain relief from the use of the drug are legally and safely able to do so whilst recreational use is still restricted.
His comments come as experts from King's College London and Australia discovered Cannabidiol (CBD) - a naturally occurring compound found in cannabis - was more effective than a placebo at reducing seizure frequency by at least 50%.
The study, published in the Journal of Neurology, Neurosurgery and Psychiatry, found some patients reported to be seizure free, though this was rare.
Cannabis oil is currently illegal in the UK, despite being available for medical purposes throughout Europe.
The Home Office has previously said it would consider a medical cannabis trial as an option for Alfie.