Former Metropolitan Police commissioner Bernard Hogan-Howe has called for an ‘urgent review’ of the evidence around the legalisation of cannabis.
Lord Hogan-Howe, who has always supported tough laws on cannabis, investigated the issue for Channel 4's Dispatches programme, to be shown on Monday.
He said if he was home secretary he would have an ‘urgent commission of experts to look at the evidence about what's happening about cannabis in North America’.
Lord Hogan-Howe said: ‘We already know from the evidence around the world that where people use it for medicinal purposes, it slides into recreational.
‘Surely it's better that we get ready for that potential change.
‘I've not seen clear evidence to say change the law now. But I have seen clear evidence to say let's review it, but in a time-limited way, not a kicking into the long grass way.
‘I think we need to get on with it, now the Government has made it easier to get medical cannabis on prescription.
‘We're lucky - we're not the pioneers and we can learn from others' mistakes. The evidence is out there and it shouldn't be ignored.’
Doctors will be able to prescribe cannabis products to patients in England, Wales and Scotland from November 1.
Home Secretary Sajid Javid decided to relax the rules on when cannabis products can be given to patients, after considering expert advice from a review following a number of high-profile cases.
A spokesman for the Home Office said the Government has ‘no plans to decriminalise recreational cannabis’.
He said: ‘The decriminalisation of cannabis would not eliminate the crime committed by the illicit trade, nor would it address the harms associated with drug dependence and the misery they can cause to families and society.
‘Decriminalisation or legalisation would send the wrong message to the vast majority of people who do not take drugs, especially young and vulnerable people, with the potential grave risk of increased misuse of drugs.'
Lord Hogan-Howe was a police officer for nearly 40 years and for nearly six years he was commissioner of the Metropolitan Police.
Cannabis: Time To End The Ban? - Channel 4 Dispatches will air on Channel 4 on Monday 22 October at 8pm.