The Royal College of Psychiatrists is to review its opposition to the legalisation of cannabis despite its concerns over the risks the drug poses to users’ mental health.

It is setting up a panel to consider decriminalisation in the wake of more countries legalising the drug and the government’s decision this summer to make medical cannabis available on prescription.

The move is critical as much of the research the government has used to keep cannabis as an illegal drug has been conducted by leading researchers from the College.

Its members also hold key positions advising ministers on mental health including the chairman of the advisory council on the misuse of drugs Dr Owen Bowden-Jones, an expert on addiction, although he is not on the panel.

The pressure for a rethink of laws on cannabis has grown since this summer’s controversy over the confiscation of cannabis oil that was being used to treat the epilepsy of Billy Caldwell, 12.

Ex-Tory leader William Hague joined some police leaders in backing decriminalisation, saying the current law on cannabis was “inappropriate, ineffective and utterly out of date.”

The Royal College of Physicians, British Medical Journal, British Medical Association and Royal Society for Public Health have also called for reform to the laws up to and including legalisation.