Russell Brand, Richard Branson, Will Self and Sting are among high-profile names to have written a letter to the Prime Minister calling for drug possession to be decriminalised.

More than 90 celebrities, health experts, lawyers and politicians have signed the letter, which was drafted by drug charity Release. It states that current prohibitive laws have led to “unnecessary criminalisation” of more than 1.5million people in the last 15 years.

It also notes that evidence from Australia, the Czech Republic and Portugal proves that health problems related to drugs are “dramatically” reduced when users are provided with medical support rather than being prosecuted.

The call for change comes as the United Nations marks it annual International Day Against Drug Abuse and Illicit Trafficking and the Support Don’t Punish organisation mark its second Global Day of Action, which highlights how drug users are still “stigmatised and abused”.