Well done, Denver: voting to decriminalise magic mushrooms is an act of common sense (even if this brave step was somewhat sullied by simultaneously voting down a pro-homeless initiative). It doesn’t mean the local Walmart is going to start flogging shrooms on two-for-one offers: it just means that the police must “deprioritise, to the greatest extent possible” any criminal penalties for Denver residents possessing or using the hippie drug of choice. It could be a life-changing move for some – growing research suggests it can help treat mental distress, such as depression and anxiety.

Denver’s move is just the latest outbreak of common sense on drugs – how depressing, then, that Britain remains so backward on the issue. That is mostly the fault, I’m sorry to say, of the Labour party. You’d expect the Tories to take a punitive, snub-the-evidence approach (even though, before assuming the Tory leadership, David Cameron accepted that drugs policy was a failure). But where is the leadership from Labour? The so-called war on drugs is a catastrophic failure, and it hurts many vulnerable people Labour was founded to represent. Drugs should be treated as a public health issue, not a part of the criminal system.

In the 1920s prohibition in the US notoriously failed to tackle alcohol use, led to lethal forms of liquor entering the black market, fuelled organised crime and its associated violence, and wasted public money. On a global scale, the “war on drugs” has been even more catastrophic. The US alone has wasted around $1tn since President Nixon unleashed this disastrous experiment, while a 2018 report by the International Drug Policy Consortium concluded that a decade-long UN global war on drugs had failed. A commitment to reduce illicit cultivation of drug crops had failed, with opium poppy production alone jumping by 130%; the number of those aged 15 to 64 using drugs at least once a year increased by 31% between 2011 and 2016.

Thousands have been executed for drug offences in this senseless “war”. Millions are criminalised: in the US alone, the number of drug arrests trebled between 1980 and 2005; and 40% of the 1.6m drug arrests in 2017 were for possession or supply of marijuana. It is dripping with racism: despite African Americans and whites having similar levels of drug use, nearly six times as many African Americans are locked up on drugs charges, while the average jailed drug offender who is black spends almost as much time in jail as a white person who has committed a violent offence. Globally, this war has led to mass destabilisation and violence. In Mexico, more than 150,000 people have died; in the Philippines, an estimated 12,000 people have died since 2016 in President Rodrigo Duterte’s own war on drugs. Thousands have died in Afghanistan’s narco war.

Here in Britain, black people are disproportionately targeted, arrested and imprisoned for drug offences, while organised and violent crime are granted a massive source of revenue. Why not learn from Portugal, where Labour’s sister party decriminalised all drug use at the start of the millennium? In the first few years of the policy, overdoses fell by 85%, and it has the lowest drug mortality rate in western Europe – a staggering 50 times lower than in the US. Drug use among those in their late teens or early 20s fell, problematic drug use fell and rates of HIV diagnoses among needle users collapsed.

While it’s good that Labour has accepted the “war on drugs” has failed and asked for the party’s members to help shape its drug policy, Labour needs to be far more courageous. This war has failed on its own terms – it destroys lives, it stops people in desperate circumstances getting the help they need, it is racist, it fuels criminality and violence.

There is no hope of the Conservatives showing any leadership on this. Labour’s refusal to commit to decriminalisation is weak: if Britain committed to a sensible, humane approach, it would represent a devastating blow to this most catastrophic of global policies. For the sake of common sense and basic humanity, Labour should say enough is enough – and publicly declare the death rites for the “war on drugs” once and for all.

• Owen Jones is a Guardian columnist