Image copyright Pioneer Image caption Those possessing cannabis can be sentenced to a maximum of five years in jail although critics argue the law is not enforced

The Liberal Democrats are backing a new report calling for the legalised sale of marijuana through licensed outlets, including "cannabis social clubs".

Criminalising cannabis use is a waste of police time, they say, and increases health risks by leaving many people in the dark about what they are taking.

The party is calling for a "regulated market" to control the pricing, potency and packaging of sales to over-18s.

The Conservatives rejected Lib Dem calls to review drug laws in coalition.

The Lib Dems' attempts to put the issue on the political agenda while in government were rebuffed by Home Secretary Theresa May, who argued existing laws were proving successful in reducing drug use and the harm associated with it.

Cannabis is currently classified as a Class B drug, with possession carrying a maximum sentence of five years in jail or an unlimited fine. Those supplying or producing cannabis face tougher penalties, with up to a maximum of 14 years in jail.

'Untold harm'

But the Lib Dems say the existing "war on drugs" has failed, diverting police resources away from tackling organised crime and that people using cannabis should not be "saddled with criminal convictions" for the rest of their lives.

The party has endorsed a new study, written by an independent panel of advisers, which calls for:

The sale of cannabis to over-18s to be legalised

Specialist, licensed stores to be set up, including "single purpose" outlets modelled on pharmacies

Cannabis to be available over the counter in plain packaging, containing health warnings

Home cultivation of cannabis to be allowed for personal use

Small scale cannabis clubs to be licensed

A new regulator to be set up to oversee the market

The report, whose authors include the government's former chief drugs adviser Sir David Nutt and Mike Barton, the Chief Constable of Durham Constabulary, argues that cannabis should be taxed according to its strength and that doing so could yield up to £1bn a year for the Exchequer.

It claims the health risks associated with cannabis use can be more effectively managed and minimised by through a "responsibly regulated market and public health interventions rather than an unregulated criminal market and punitive criminal justice response".

The Lib Dems will decide whether to adopt the proposals as party policy at its Spring Conference this weekend.

What is the UK's drug policy?

Image copyright Science Photo Library

Under the Misuse of Drugs Act 1971, illegal drugs are divided into Class A, B and C. Penalties are most severe for Class A drugs like crack cocaine and heroin, and least severe for Class C drugs like khat and anabolic steroids.

Producing or supplying a Class A drug can be punished with life imprisonment, while there is a 14-year maximum term for Class B and C.

Possession is treated less severely, with maximum sentences of seven, five and two years for Class A, B and C respectively. Warnings and on-the-spot fines are sometimes given for possession of drugs. Read more

"Every year, billions of pounds are put into the pockets of organised criminals selling cannabis, and vast amounts of police time and resources are wasted, going after those using the drug," said its health spokesman Norman Lamb.

"It is not good enough to continue pretending that everything is OK, or that the current system is working. Millions of British citizens are using cannabis with no idea of the potency of what they are taking.

"The current system is doing untold harm: on health grounds and on justice grounds. Leaving the cannabis market in the hands of criminals puts people's health at risk, and criminalises people, blighting their careers."

Steve Rolles, an analyst at the Transform Drug Policy Foundation - who chaired the panel - said the debate was no longer theoretical as cannabis had been legalised for recreational use in a number of US states and that Canada would soon follow suit.

"Over the decades politicians have done great work in cross party settings to explore alternatives to criminalisation and we hope that our report will further assist in taking some of the heat out of the debate," he said.

The Home Office has said it has no plans to change the law, insisting there is "clear scientific and medical evidence that cannabis is a harmful drug which can damage people's mental and physical health, and harms individuals and communities".