There is a great irony in the government’s continued support for drug prohibition. It is founded on the claim that people must be protected from harm, yet the effect of their approach is precisely the opposite. Indeed, the government itself, and many others around the world, stands accused of directly putting children and young people at great risk of harm.

So, my support for reform is based on a harm reduction approach. As a liberal, I also make the case for an individual’s freedom to make their own decisions about what they want to do, provided it does not harm others. But you don’t have to be convinced by that principle. Just consider the impact of our current approach, and you will conclude that it is reckless and irresponsible.

First, drugs are everywhere. The so-called war on drugs has failed miserably. Opponents of reform will often point to teenagers whose lives have been ruined, for example, by smoking potent strains of skunk. Yet this is happening here and now with cannabis prohibited. It’s happening because supply is in the hands of criminal networks. It’s happening because teenagers have no idea what they are buying and whether it is contaminated. So, leaving the supply of cannabis in the hands of criminals is stupid and dangerous. It does nothing to protect young people from harm, but it does put them at risk of harm.

Second, with every additional gram of cannabis sold, more money goes to criminals – individuals who certainly won’t pay tax on their earnings. How ridiculous is that?

During the coalition, the Liberal Democrats commissioned the Treasury to undertake an analysis of the potential tax revenues which would flow into government coffers if cannabis were legal and regulated. Up to £1bn a year was the answer. Instead of enriching organised crime, this money could do good – extra funding for the NHS, social care, education or the police, for example.

But there are other awful consequences of prohibition. Given just how profitable the drugs trade is for organised crime, it is important to defend your market. They can’t issue a writ in the high court if they are faced by a competitive threat. So they depend on the use of extreme violence. And this impacts most heavily on the most deprived communities, with children and young people sucked into the drugs trade, putting them at enormous risk.

Just recently there was a news report of unscrupulous adults encouraging vulnerable children to take knives into school in order to get them excluded so they could then be exploited. Week after week we get horror stories of “county lines” – the despicable practice of using children to traffick drugs into rural areas. This is child exploitation of the worst sort when children are living in fear of drug masters, petrified of breaking rank for fear of violence or something even worse.

Too often the exploited children are treated as culpable, yet they are victims of a disgusting trade facilitated by government policy. When will we start to recognise the link between the illegal drugs trade and youth violence? When will we start to understand that there is a better way of confronting these horrors?

And then there is the fact that we still prosecute more than 10,000 people every year for possession of cannabis, let alone other drugs. A caution is enough to damage your career prospects – for doing something that half the cabinet have probably done at some point in their lives. The hypocrisy beggars belief – indeed, the most dangerous drug of all, in terms of harm to oneself and others, alcohol, is consumed in vast quantities in our national parliament. And yet the government and the Labour party continue to support the criminalisation of fellow citizens for using cannabis, which is less dangerous.

I am instinctively hostile to drugs, both legal and illegal, because I fear the dangers of consuming any drug in significant quantities. But I know that the present approach is a catastrophic failure. I know that the best way to protect young people from harm is to, first of all, legalise and regulate cannabis. Let’s follow the rational approach of the Liberal government in Canada, and let’s have an informed discussion about how best to reduce the harm caused by other drugs.