Some people think the Lib Dems are potty after they unveiled one of the most radical policies of the general election campaign so far.

The party, led by Tim Farron , said it would legalise cannabis and allow it to be sold openly if it wins.

The plan is to “break the grip of criminal gangs” through the creation of a “legal, regulated market” while raising up to £1billion in tax.

So is it more than just a pipe dream?

High time

Senior policy analyst at Transform Steve Rolles reveals the benefits of legalising cannabis

Criminalising cannabis has been a total disaster.

Enforcing cannabis prohibition is expensive, with ­estimates putting the cost at around £500million a year.

But what have the billions spent and millions criminalised over the years achieved? Very little.

Cannabis is easily available to anyone who wants it, including kids, whether on street corners or via online “dark net” markets.

The Home Office ’s own inter-national study found no link between tougher enforcement and levels of drug use. Prohibition puts a huge drain on scarce police resources and it just doesn’t work.

There is no link between tougher enforcement and levels of drug use (Photo: Getty)

But it’s worse than that. What cannabis prohibition has achieved is to gift control of a market worth billions each year to organised crime and unregulated dealers.

This criminal market is closely associated with child slavery and human trafficking.

It also criminalises millions across the country, with tens of thousands getting a criminal record each year.

Yet probably a quarter of adults have tried cannabis, a crime punishable with up to five years’ jail and an unlimited fine.

The criminal market has also fuelled the emergence of ever more potent varieties of cannabis – the “skunk” that now dominates.

It’s more profitable for dealers but also more risky for the users who now cannot access milder, safer cannabis even if they want to.

Cannabis prohibition also created the market opportunity for Spice, a synthetic drug that is far more potent and toxic than the herbal cannabis it mimics.

Prohibition puts young people in danger from gangs (Photo: Reuters)

Originally a legal high, Spice has now also been banned, demonstrating a depressing failure to learn lessons of the past.

Prohibition created the spice problem, so who seriously thought more prohibition would be the solution?

Unsurprisingly, the market for Spice has simply moved from head shops to unregulated criminal street markets, becoming yet more potent and dangerous and now wreaking havoc in prisons and among the homeless .

Far from protecting communities and young people, ­prohibition puts them in danger, from gang violence, more risky drugs and a criminal record that can blight their lives.

Given this catastrophic failure, it is high time for a rethink. It is clear the market cannot be wished away or eradicated by force.

So we face a choice. We can leave it in the hands of organised crime or we can take back control and establish a regulated legal framework to manage the market and minimise its potential harms.

Tim Farron has pledged to legalise and regulate cannabis (Photo: PA)

The independent expert group I chaired, with the help of former Government drugs tsar Professor David Nutt and senior police and academics, was asked to make recommendations on how a regulated market could work to deliver on youth protection and reduced crime.

We looked at reforms from around the world where cannabis legalisation is becoming a reality.

Eight US states, including California, have already legalised, joining Uruguay, Jamaica, the Netherlands, and Canada.

We also drew on important lessons from the successes and failures of alcohol and tobacco regulation.

We were acutely aware of the tension between the interests of big business and the need to protect health.

Drugs are not normal products, like groceries. So we proposed that while there should be regulated access to herbal cannabis for over-18s via licensed vendors, there should also be controls on potency and restrictions on advertising and marketing – as with tobacco.

Legalising cannabis will push criminals out of the market (Photo: Getty)

No one wants to see the sort of promotion we still have with alcohol, like cannabis sponsorship of football teams.

Cannabis should be available to adults but not aggressively promoted.

We also proposed that money saved across the criminal justice system could be redirected to other policing priorities while tax revenue from the market – potentially up to £1billion a year – could boost drug education and treatment.

People often talk about sending out the right message on drugs and worry about what message legalisation would send.

But criminal law is not the right tool to educate young people on healthy lifestyles. It just doesn’t work, only criminalising and ­alienating the very people we are trying to reach.

Legal cannabis control will better protect young people and push criminals out of the market.

We call on all parties to stop their “tough on crime” posturing and do the responsible thing: take control of cannabis and other drug markets.

• Transform is a charitable think-tank that campaigns for the legal regulation of drugs in the UK and inter-nationally.

2.1m took a toke in last year

• 6.5% of UK adults used cannabis in the past year, some 2.1 million people. Globally, the number is 182 million people
• In 2015, 27,462 people got criminal records for cannabis possession and more than 1,000 people have been sent to prison annually for cannabis offences.
• Since cannabis was legalised in Colorado in 2012, possession arrests have fallen by 80% but youth use has not risen.
• Colorado’s legal cannabis market generated more than £77.6million in tax revenue in 2016. Estimates have suggested that the UK market could generate between £500million and £1billion.