The central mystery of the modern state is this. The necessary resources, both economic and political, will always be found for the purpose of terminating life. The project of preserving it will always struggle. When did you last see a soldier shaking a tin for a new rifle, or a sponsored marathon raising money for nuclear weapons? But we must beg and cajole each other for funds whenever a hospital wants a new dialysis machine. If the money and determination expended on waging war with Iraq had been used to tackle climate change, our carbon emissions would already be in free fall. If as much money were spent on foreign aid as on fighter planes, no one would ever go hungry.

When the state was run by warrior kings, this was comprehensible: they owed their existence to overwhelming force. Now weapons budgets and foreign wars are, if anything, an electoral liability. But the pattern has never been broken.

In Geneva today, at the new review of the conventional weapons treaty, the British government will be using the full force of its diplomacy to ensure that civilians continue to be killed, by blocking a ban on the use of cluster bombs. Sweden, supported by Austria, Mexico and New Zealand, has proposed a convention making their deployment illegal, like the Ottawa treaty banning anti-personnel landmines. But the UK, working with the US, China and Russia, has spent the past week trying to prevent negotiations from being opened. Perhaps this is unsurprising. Most of the cluster bombs dropped during the past 40 years have been delivered by Britain's two principal allies - the US and Israel - in the "war on terror". And the UK used hundreds of thousands of them during the two Gulf wars.

Cluster munitions are tiny bombs - generally about the size of a drinks can - packed inside bigger bombs or artillery shells. They scatter over several hectares and they are meant to be used to destroy tanks and planes and to wipe out anti-aircraft positions. There are two particular problems.

The first is that the bombs, being widely dispersed, cannot be accurately targeted. The second is that many of them don't detonate when they hit the ground. Officially, cluster bombs have a failure rate of between 5% and 7%. In reality it's much higher. Between 20% and 25% of the cluster munitions Nato forces dropped during the Kosovo conflict failed to go off when they landed. The failure rate of the bombs dropped by the US in Indochina was roughly 30%. Of the cluster bombs that Israel scattered over Lebanon, 40% did not detonate.

The unexploded bombs then sit and wait to be defused - leg by human leg. They are as devastating to civilian populations as landmines, or possibly worse, because far more of them have been dropped. Even 30 years or more after they land - as the people of Vietnam and Laos know - they can still be detonated by the slightest concussion.

A report published last week by the independent organisation Handicap International estimates that around 100,000 people have been killed or wounded by cluster bombs. Of the known casualties, 98% are civilians. Most of them are hit when farming, walking or clearing the rubble where their homes used to be. Many of the victims are children, partly because the bombs look like toys. Handicap's report tells terrible and heartbreaking stories of children finding these munitions and playing catch with them, or using them as boules or marbles. Those who survive are often blinded, lose limbs or suffer horrible abdominal injuries.

Among the case histories in the report is that of a family in Kosovo who went to swim in a lake a few kilometres from their village. One of the children, a six-year-old called Adnan, found a metal can on the bank and showed it to his family. It exploded. His father and older brother were killed and Adnan was gravely wounded. His sister later returned to the lake to collect the family's belongings, stepped on another Nato cluster bomb and was killed.

The economic effects of cluster bombs can also be deadly. Like landmines they put many agricultural areas out of bounds, because of the risk of detonating one while ploughing or harvesting. In some parts of Lebanon the fields have remained unharvested this year. Cluster bombs dropped on to the rubble of Lebanese towns have made reconstruction slow and dangerous.

The numbers of cluster bombs deployed are mind-boggling. The US air force released 19m over Cambodia, 70m in Vietnam and 208m in Laos. Over much shorter periods, the US and the UK dropped some 54m cluster bombs on Iraq during the 1991 Gulf war and around 2m during the 2003 Iraq invasion. Israel scattered 4m cluster bombs over Lebanon during its latest invasion earlier this year, almost all of them during the final 72 hours. It looked like revenge, or an attempt (like its deliberate bombing of the Jiyeh power plant, causing a massive oil spill) to cripple Lebanon's economy. Since the invasion, more than two Lebanese civilians have been blown up by cluster bombs each day on average.

The only other nation which has used cluster bombs extensively since the second world war is Russia, which dropped large quantities in Afghanistan, and which scatters them in Chechnya, sometimes deliberately bombing market places and other civilian targets. Apart from that they've been deployed in small numbers by Sudan, Libya, Eritrea, Ethiopia, Nigeria, Serb forces, Hizbullah and warring factions in Tajikistan. What good company we keep.

These weapons are arguably already illegal. A protocol to the Geneva conventions prohibits attacks which "are of a nature to strike military objectives and civilians or civilian objects without distinction" and "which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated". I think 98% would be a fair definition of "excessive".

But their deployment will continue until there is a specific treaty banning them. It's clear the US and UK governments know their use is wrong. Handicap International reports that the Coalition Provisional Authority (the administration set up by the US to govern Iraq in 2003) "strongly discouraged casualty data collection, especially in relation to cluster submunitions". During a debate in the House of Lords last month, the Foreign Office minister, Lord Triesman, made such a feeble show of justifying their use that you couldn't help suspecting he was batting for the other side. The only justification he could find was that, unlike landmines, cluster bombs are not intended to lie around undetonated.

Two days ago, a letter sent to the defence minister by the international development secretary, Hilary Benn, was leaked to the press. He argued that "cluster munitions have a very serious humanitarian impact, pushing at the boundaries of international humanitarian law. It is difficult then to see how we can hold so prominent a position against landmines, yet somehow continue to advocate that use of cluster munitions is acceptable."

But Benn appears to be alone. The foreign office maintains that "existing humanitarian law is sufficient for the conduct of military operations, including the use of cluster munitions, and no treaty is required". The government seems unable to break its habit of killing.

Monbiot.com