Since the first day here at the negotiations in Dublin the UK has appeared determined to undermine efforts to achieve an effective and comprehensive international treaty banning cluster munitions. It is becoming increasingly hard to see how the Oslo process is going to come up with a good treaty - at least one with the UK on board - unless the British delegation starts to compromise. Without having Princess Diana championing humanitarianism, as in the days of the mine ban treaty, getting the UK on board has been akin to dental surgery without an anaesthetic.

For sure, in diplomacy it takes time for directions to filter down from policymakers to the diplomats, but time is running out. We have a week left and it looks like the UK delegation has not even read the newspapers. Prime minister Gordon Brown's widely reported pre-by-election statement this week asking the defence ministry to review its position on clusters indicated a shift, but the UK delegates have remained unmoved. Brown might want to call them up. Then again, his apparent concession may just have been an election gimmick, in which case shame on him.

Cluster munitions leave de facto landmines when their duds scatter, often over a wide area. Today they cause a far greater threat to civilian lives and livelihoods than land mines. With 156 states party to the Mine Ban Treaty, the world has already agreed mines are illegal. Their use has been so stigmatised that even non-parties to the treaty like the US, China and Russia are reluctant to use them.

Clusters, however, are still used in massive numbers. It is hard to imagine the deadly legacy of one million cluster duds hidden in the homes, gardens, and fields of southern Lebanon. I tiptoed through those terrifying booby-trapped killing fields in the course of investigations for Human Rights Watch. It will take years of work to clear the land of the bitter fruit of conflict. They maim and kill, but they also mean you cannot farm the land or walk the fields.

Imagine if the green and pleasant pastures of England were suddenly off limits, the hospitals filled with injured, the morgues with the dead. And even when life started to turn around, the farmers had to sit idly by contemplating their unplanted fields, unable to make a living for fear of stepping on a hidden bomb.

There is a macabre surrealism to listening to the delegations of so-called "like-minded states" talking about the enormous exemptions they want to ram through in this treaty. Some delegations use terms like "dangerous duds" as if every live bomb were not dangerous. But this "like-minded" bloc looking for maximum exemptions is crumbling. Only the UK is really holding on to a no-compromise position.

The UK is fixated with "self-destruct devices", insisting that they work. But the simple fact is that self-destruct mechanisms do not work. In Basra and Lebanon the vaunted M85 cluster munitions failed so miserably their dud rate was 10 times higher than advertised. It is absurd to claim that these munitions don't cause unacceptable harm to civilians.

I have to wonder if the members of the British delegation or their political masters would be comfortable with their children playing in the fields of southern Lebanon. I am scared to walk even in the cleared areas - and I am a grown-up with a soldier's training.

The British delegates here say their cluster rockets are "different" because they fly straight and the pilot sees where they are aimed, and instead of covering a football field they only cover an area the size of a few homes. And with only nine sub-munitions the rockets cannot be so bad as the bombs with over 600. That is all very well and good. But you don't fire just one, and an Apache carries enough rockets for a volley of 684 cluster munitions in total. And the effect is the same - when they strike they explode over a target raining down over an area, no matter the size, and leave unexploded duds behind.

It is clear the US is pushing the British government hard to insert a massive loophole in the treaty that would allow parties to conduct joint military operations with non-parties even if those non-parties used clusters in joint operations. The UK is thus trying to shape the treaty to say cluster munitions are so bad they must be illegal, but if the US uses them, then Britain must be allowed to help. This is nonsense.

Before it is too late, the UK needs to start showing some humanitarian principles and some political backbone. As a close ally of the US and a major military player on the global stage, it is important that the UK remains on board the Oslo process. But it is also essential that the UK follow up on Brown's helpful statement this week and drop its efforts to drive an American coach and horse through the treaty. Rather than standing up for narrow US interests, the UK needs to start standing for the interests of the victims - past, present and future - of these horrible weapons.

Marc Garlasco is the senior military analyst at Human Rights Watch (HRW). As well as being HRW's resident expert on battle damage assessment, military operations, and interrogations, Marc also leads HRW's work on prisoner abuse, civilian military contractors, and non-lethal weapons. Marc was in Lebanon during the 2006 war and did an exhaustive investigation into the use of cluster munitions there. Before coming to HRW, Marc spent seven years in the Pentagon as a senior intelligence analyst covering Iraq. His last position there was chief of high-value targeting during the Iraq war in 2003. Marc was on the Operation Desert Fox (Iraq) Battle Damage Assessment team in 1998, led a Pentagon Battle Damage Assessment team to Kosovo in 1999, and recommended thousands of aimpoints on hundreds of targets during operations in Iraq and Serbia. He also participated in over 50 interrogations as a subject matter expert.

© 2008 The Guardian