The war on drugs has failed - that's what more than 90 celebrities, politicians, lawyers and health experts have written to the prime minister in an urgent call for a review of the government's policy on illegal drugs.
Recent reform victories are reshaping the landscape of the oldest debate in drug policy, and now, the letter - which was drafted by the drug charity, Release - has emphasised the need for change.
Celebrities including comedian Russell Brand, musician Sting, Sir Richard Branson and author Will Self, are demanding a shift in drug legislation so that possession is no longer a crime in the UK.
The signatories of the letter to David Cameron also include MPs like Caroline Lucas and groups involved in law enforcement, such as the Prison Governors Association and the National Black Police Association and the barrister Michael Mansfield QC.
The letter says the use of legal sanctions for the possession of drugs in the UK has led to the "unnecessary criminalisation" of more than 1.5 million people in the last 15 years.
Ms Lucas said the time has come to acknowledge that the UK’s drug laws are "outdated, ineffective, and enormously costly.
"The evidence shows that, as a first step, treating drug addiction as a health issue, rather than a criminal one, would significantly reduce the social and individual harms associated with criminalisation. It’s time to face up to the facts: the system is broken and it’s time for reform.”
The letter also highlights the social and economic costs of pursuing a criminal justice response that impacts primarily on young people who receive criminal records that limit their employment and educational opportunities.
The call comes as part of a global day of action against the so-called "war on drugs" and protests are planned to take place in 100 cities on Thursday.
Cities including Paris, Warsaw, Mexico City and Rome will be calling for action, while in London there is expected to be a public gathering in Parliament Square where a billboard has been erected to face Parliament which will "underscore the Prime Minister’s inaction on drug policy."
"The global day of action is a public show of force for drug policy reform", said Ann Fordham, who is executive director of the International Drug Policy Consortium, which focuses on issues related to drug production, trafficking and use.
"The tide is turning and governments need to urgently fix their drug policies and repair the damage that has been done," she said.
The letter goes on to state that evidence from Australia, the Czech Republic and Portugal shows that health problems linked to drugs are "dramatically" reduced when users are given medical support and advice rather than being prosecuted.
Niamh Eastwood, Executive Director of Release, the organisation leading the action stated that as the drug policy reform debate has moved forward in recent years "the UK government needs to be at the forefront of it. "
"In 2002 when the Prime Minister was a member of the Home Affairs Select Committee he supported the recommendation that the UN consider alternatives to the status quo.
"We are asking him to stand by that commitment and recognise the damage that has been done, both nationally and internationally, by repressive drug policies”.
The British Medical Association (BMA) faced a fierce backlash from a drug policy expert this week after they voted down a motion that would push for the legalisation of cannabis in the UK.
In what has been called a "very strange" move, doctors at the BMA's annual representative meeting in Harrogate dismissed calls for drug legalisation to instead call for anyone born after the year 2000 to be banned from ever buying cigarettes.
One of the experts who advised the Uruguayan government on its landmark decision legalise cannabis told The Huffington Post UK that drug reform is now necessary in the UK.
Steve Rolles, the Senior Policy Analyst for the Transform Drug Policy Foundation, branded the BMA's reaction to the motion "both unscientific and unethical."
"Using punishment and mass criminalisation of young people as a public health strategy is an very odd thing for the BMA to endorse," he said.
"It effectively means directing resources away from proven health interventions into ineffective criminal justice enforcement.
"It's a position that is both unscientific and unethical. Doctors should 'first do no harm', yet 50 years of prohibition shows it is profoundly harmful."