Dame Sally Davies, the Chief Medical Officer for England, said it was now difficult to defend the retention of cannabis as a Schedule 1 drug - meaning it was considered to have little or no therapeutic potential - on scientific grounds.
Her decision is the first part of a review commissioned last month by Home Secretary Sajid Javid into the medicinal use of cannabis.
The Advisory Council for the Misuse of Drugs will now issue an assessment within the next three weeks on whether it should be re-scheduled.
The review was originally launched in response to a number of high profile cases involving children being denied the use of cannabis for the treatment of epileptic seizures, including Alfie Dingley and Billy Caldwell.
In her report, Dame Sally said the evidence relating to the medicinal use of cannabis had been reviewed and considered "robust" by leading international scientific and regulatory bodies, as well as the World Health Organisation.
She recommended the re-scheduling should include synthetic cannaboids which potentially have greater therapeutic benefits with less potential for harm.
"There is now however, conclusive evidence of the therapeutic benefit of cannabis based medicinal products for certain medical conditions and reasonable evidence of therapeutic benefit in several other medical conditions," she said.
Dr Adrian James, Registrar at the Royal College of Psychiatrists said: “We fully support a review that may lead to improved treatment for patients.
“Cannabis products for medicinal use that have been properly reviewed, and approved by the National Institute for Health and Care Excellence, can have significant health benefits.”
Ian Hamilton, Lecturer in Mental Health, University of York, added: “This is welcome news, particularly for the potential rescheduling of cannabis, as it will make research easier which is critical for the evidence base to develop. Most studies are based on small samples or of poor quality.”