I have spoken out on many issues during my career, but there is one that leaders in poorer countries passionately lobby me to campaign on: the prohibition of drugs.

The “war on drugs” is harming the most vulnerable and criminalising poverty. It is not a war on drugs – despite decades of prohibition, drug production and consumption is on the increase globally – it is a war on the poor. Prohibition damages people and the planet.

It is also a staggering waste of money. The cost of enforcing the war on drugs is in excess of $100bn (£77bn) a year. This rivals the size of the global aid budget (about $146bn). If redirected, that money could help provide healthcare, education and clean water to people across the world.

Drugs policies make our world a more dangerous place, not a safer one: whether that’s by handing immense wealth and power to organised criminals, causing violent policing of poor communities, or ensuring consumers have little idea what they are taking.

On Tuesday, Health Poverty Action launches a report exposing the human stories from the streets of Brazil and the fields of India. Punishing Poverty provides a platform for the voices on the ground behind the overwhelming evidence that current drug policy is felt most sharply by poor communities. It traps people in a cycle of poverty and inequality for generations.

Testimonies gathered in Brazil show those orchestrating and profiting from the trade at higher levels are largely ignored, while the poorest face threat of arrest, imprisonment and even death. Similarly in India, forced eradication, fines, imprisonment and violence are not deterring small-scale farmers from cultivating illicit opium poppies to keep their children from starving, when they feel they have no other choice. We live in a world where people will work to support their families. They will take risks in the absence of options.

To break the cycle, we need to reverse this oppressive trap. We must campaign for a complete reform of drug policies, and look at legal regulation of the drugs trade to make it safer and lives more stable, from producer to seller to consumer.

The good news is, this has begun.

Cressida Dick is right: the middle class need to realise drugs cause misery Read more

Portugal has seen dramatic drops in problematic drug use, and HIV infection rates, by decriminalising all drugs. If we were to go further and legally regulate drugs we could make them safer still, removing the power from criminal gangs, controlling who can buy drugs, where, and in what quantities.

It would also mean we would have the option to tax them and raise vital revenue for development and public services.

This shift is happening. In 2013 Uruguay became the first country to fully legally regulate cannabis, followed by Canada last year. Ten US states and the District of Columbia have done the same. California’s approach to cannabis legalisation safeguards small-scale farmers and pardons those with previous cannabis-related offences. And this is important, because how policy is done matters to all those involved.

Facebook Twitter Pinterest A demonstration in favour of legalising marijuana in Montevideo in December 2013. That year Uruguay became the first country to legalise its sale, to tackle drug trafficking and related crime. Photograph: Pablo Porciuncula/AFP/Getty Images

In the shift to legal, regulated models, the development sector must protect the most vulnerable. Those who have been most at risk of poverty and exploitation during prohibition will still be at risk in a post–prohibition world if multinational corporations take over from where the cartels and criminal gangs leave off. The whole market needs regulating to protect health and reduce poverty.

We have the opportunity to ensure reforms are implemented within a social justice model in collaboration with affected communities. At the same time, we can tackle those social and economic problems that drive people into the trade in the first place.

Legally regulating drugs isn’t radical, it’s responsible. Drugs are too dangerous not to be regulated, and too profitable not to be taxed.