Some look like torch batteries. Others resemble tennis balls or cans of orange juice, trailing coloured ribbons. They are easily mistaken for toys, which is why so many of those who are maimed or killed by cluster bombs are small children. They have been used in most conflicts since the Second World War, when German butterfly bombs fluttered down on London. With their affection for euphemism, Americans call them "firecrackers" or "popcorn". They are hollow shells, containing anything from three to more than 2000 bomblets that can spread over large areas and lie dormant for decades. The campaign to outlaw them gained support last year in the wake of the Israeli bombardment of southern Lebanon which, according to the UN, left 100,000 unexploded bomblets scattered across villages, farms and open countryside. This was despite an undertaking from Israel to the American manufacturers that they would not be deployed in civilian areas. Yesterday 46 nations, including Britain, took a small step towards outlawing these ruthless killers by calling for a treaty to ban them.

The news comes as a pleasant surprise to those who believed that the British government's motive in attending the Oslo conference was to water down any international attempt to create a ban. The US, Russia, China and Israel were significant absentees and, until now, the official British position has been aligned with theirs. Britain has been a major producer, stockpiler, user and exporter of cluster bombs. Our forces used them in Iraq in 2003, Kosovo in 1999, during the first Gulf War in 1991 and in the Falklands in 1982. Last year Foreign Office minister Lord Triesman told the Lords that they "provide a unique capability . . . for which other munitions are not necessarily practical", shortly before Britain supported the blocking of a proposed ban at UN arms talks in Geneva. This was an untenable and dishonourable position. As many as 98% of the casualties caused by cluster bombs are civilians, a clear contravention of the Geneva Convention. It is also inconsistent to have taken a lead in the banning of landmines in 1997, following the high-profile support of the late Princess of Wales, yet support the continued use of cluster bombs.

Although yesterday's declaration is non-binding, it is essential that Britain follows through on its commitment. Revulsion at pictures of napalm victims in Vietnam put an end to its use as an incendiary weapon. The lesson of the landmine campaign is that public outrage, a well-informed debate and appropriate celebrity endorsement can stigmatise such weapons to the point where even those countries that do not sign up to a ban no longer deploy them. The next challenges will be to define what is meant by a cluster bomb, without loopholes for callous governments to exploit, and devise a strategy to help countries infested by them. Britain should take the lead and make a firm commitment now to outlaw cluster bombs, rather than being shamed into action by others. In modern warfare, fought cheek by jowl with civilian populations, there is no place for these indiscriminately murderous weapons.