Sir Sadiq Khan has backed calls for the possession of small quantities of natural cannabis to be decriminalised, saying current rules “cannot be justified”.

The Mayor of London said a report by the independent London Drugs Commission (LDC) published on Wednesday had provided “a compelling, evidence-based case” for decriminalisation and urged the Government to consider the move.

Set up by Sir Sadiq in 2022 and chaired by former lord chancellor Lord Charlie Falconer, the LDC found the current laws on cannabis were “disproportionate to the harms it can pose” following a study of how the drug is policed around the world.

It also found cannabis policing “continues to focus on particular ethnic communities”, damaging relations between the police and those communities.

The commission stopped short of calling for full decriminalisation, saying the long-term harms to public health were “not yet well understood”.

Instead, Lord Falconer’s committee called for “natural” – as opposed to “synthetic” – cannabis to be moved from the Misuse of Drugs Act to the Psychoactive Substances Act, effectively legalising possession of small amounts for personal use while continuing to prohibit importing, manufacturing or distributing the drug.

They also called for improved addiction services and greater education for young people on the dangers of cannabis.

Lord Falconer said: “Legalisation is not the answer. The criminal justice system response needs to focus only on the dealers and not the users.

“Those who suffer from the adverse effects of cannabis – which may be a small percentage of users but it is a high number of people – need reliable, consistent medical and other support. And there needs to be much more education on the risks of cannabis use.”

Under current laws, cannabis is a class B drug and those found in possession face a fine or imprisonment.

LDC deputy chairwoman Janet Hills, a former Metropolitan Police detective, said the report was “a driver for change in our community” and called for “a more balanced and compassionate approach to policing in our city”.

Responding to the report, Sir Sadiq said: “I’ve long been clear that we need fresh thinking on how to reduce the substantial harms associated with drug-related crime in our communities.

“The London Drugs Commission report makes a compelling, evidenced-based case for the decriminalisation of possession of small quantities of natural cannabis which the Government should consider.

“It says that the current sentencing for those caught in possession of natural cannabis cannot be justified given its relative harm and people’s experience of the justice system.

“We must recognise that better education, improved healthcare and more effective, equitable policing of cannabis use are long overdue.”