Johann Hari: Why is Britain allowing money and weapons to pass into the hands of right-wing militias?

Here are clues to why the wars in Afghanistan and Iraq have hit their current dead-ends

On the website of the British Foreign Office, a small photograph recently appeared. It shows Kim Howells, our Foreign Office minister, looking into the camera, smiling, as he is surrounded by gun-yielding men accused of murder. He had not been taken hostage. No: he was there to represent a government that gives these men money and military aid.

By tracing the story of this photograph, we can trace the worst aspects of British foreign policy – and find clues to why the wars in Afghanistan and Iraq have crashed into their current bloody dead-end.

Howells was in Colombia, a country locked in one of the nastiest civil wars of the past century. It began more than 40 years ago, when some parts of the hungry, mixed-race majority began to fight against the fact that a tiny, white, land-owning elite held virtually all the country's wealth. Since then, it has hardened into a conflict between two gnarled human rights-abusing wings.

To the left, there are a slew of guerrilla groups – most prominently the FARC and the ELN – who fund themselves by kidnapping, extortion and "taxing" drug-producers.

To the right, there is the Colombian government and the right-wing paramilitary death-squads it has unleashed against any community of civilians suspected of leftish sympathies, or of challenging the elite. That's why to be a trade unionist in Colombia – organising for better wages and working conditions for your colleagues – is to carry a tombstone on your back: more are murdered there than in the rest of the world combined. Between them, these violent wings have killed more than 30,000 people and driven three million people from their homes.

Howells – our representative – was posing with some of those alleged to be the worst abusers. He was huddled with the High Mountain Brigades, who Amnesty International says have been involved in hunting down and murdering trade unionists.

Here's what our taxes help deliver to ordinary Colombians. On 10 January, at 10.30am, Colombian soldiers wearing balaclavas burst into the house of Rosa Maria Zapata, a 56-year-old indigenous woman. When the soldiers pointed their guns at her and barked that they wanted to know where the guerrillas were, she screamed back that she didn't know; she doesn't know any guerrillas. They told her she was hiding weapons for the FARC. They told her they knew. She howled and protested. So they started searching – and a moment later she heard gunfire. The police announced they had killed the guerrilla. She went running – and found her severely disabled 22-year-old son dead.

The British pro-peace group Justice for Colombia believes these soldiers received British training. They have documented 36 other civilians murdered by potentially British-trained forces in a six-month period, and they are asking the Foreign Office to outline exactly where our money goes.

How has Kim Howells responded? Easy. He says his critics "support FARC, a band of gangsters and drug smugglers", and that FARC is responsible for "most" of the murders in Colombia. In reality, Justice For Colombia is supported by more than half of all Labour MPs, and opposes all violence within Colombia. And the FARC – while unequivocally disgusting – is responsible for far fewer murders than the government and right-wing death squads, according to every major study.

So how did this happen? How did a minister in a Labour government end up parroting the propaganda of the Colombian hard-right? The British government says they have become the second biggest military donor to Colombia – after the US – because they want to promote human rights there. But if you had a few million pounds to support human rights in that country, the idea you would support the High Mountain Brigades is simply surreal.

No – the explanations for British backing lie elsewhere. The first is a desire to support the United States, because we project our power by being a loyal adjunct to American military might. If Britain wasn't offering these funds, the Bush administration would be alone in the world in backing the Colombian military.

We also do it to support the global "war on drugs". Since Bill Clinton's presidency, the US has been spraying hundreds of thousands of tonnes of chemical poisons onto the vast tracts of Colombia where the coca leaves essential for cocaine production are grown. All plants and trees die in their wake. Birth defects and cancer rates are rising. And the effect on drug production? It simply moves to another area. Drug production is so profitable and so popular that it cannot be fumigated off the face of the real world. Drug prohibition simply hands great swathes of the Colombian economy to armed criminal gangs, from the FARC to the right. It ensures they will always have enough money to buy enough guns to preserve their patches of territory.

There is another way. More and more Colombians believe it is only by bringing drugs into the legal economy – where they can be controlled and taxed by the state – that the guerrillas and paramilitaries can be stripped of their cash-flow. From the current Conservative Interior Minister, Carlos Holguin, to the former Attorney, General Gustavo de Greiff, to the country's most popular singer, Juan Esteban Aristizabal, it is being argued that an end to drug prohibition is the only long-term solution to the civil war. Yet Britain demands the opposite.

There is one more crucial reason why we are supporting the Colombian military. The British oil firm BP controls half of Columbia's petrol output. The historian Mark Curtis argues the UK is keen to ensure resources "remain in the correct hands" – that is, "our" hands. In a highly unequal country angry at seeing its resources siphoned off by foreigners, that means supporting an elite who are willing to keep the majority in their place.

These three factors can help us to understand why the military actions in Afghanistan and Iraq have gone so wrong. As in Colombia, we got in, in large part, out of loyalty to the US. As in Colombia, we are inflicting the "war on drugs" on Afghanistan. If we turned up in any country and announced that we were there to destroy 40 per cent of their economy, the people would fight back. This is why we are losing southern Afghanistan even to the hated Taliban.

And as in Colombia, the US-UK Coalition has misgoverned Iraq so catastrophically because it has been primarily driven by a desire to ensure that control of the country's resources went to the Right People. The protection of the Oil Ministry, while Baghdad's museums and hospitals and universities were looted and burned all around it, is only the most bleak symbol of this.

The image of Kim Howells squatting with a unit who are alleged to have tortured and butchered trade unionists can be seen as a Rosetta Stone for the dark side of our foreign policy. It is a reminder that, if we want to turn Britain into a force for human rights in the world, we have to campaign long and hard to turn much of it around. If we don't, it will end with more women like Rosa Maria Zapata, clutching her dead disabled son and asking why.

j.hari@independent.co.uk