THEY have been described as "beautifully, magnificently lethal". A single British Apache attack helicopter can launch 684 cluster bombs, known as M73 sub-munitions, in one furious volley of rocket fire. The bomblets rain down creating a "kill zone" which renders the entire area impassable for any soldier, tank or truck - or any passing civilian or family car, for that matter.

Each Apache chopper is fitted with four rocket pods, containing 19 rockets, and each rocket holds nine M73 cluster bomblets. In the face of global opinion, the UK wants to see the M73 granted exemption from prohibition at next month's Dublin summit at which 100 nations will try to force through a total ban on cluster bombs.

Another cluster bomb the British government wants to see saved is the M85 - used to devastating effect by UK forces in and around the southern Iraqi city of Basra in 2003, and by Israeli forces in southern Lebanon. The UN's unexploded ordnance clean-up operation after the Israel-Hezbollah war in the summer of 2006 identified more than 960 strike sites, and cleared 137,000 unexploded cluster bombs, including 1500 M85s. By late 2007, 220 injuries and 40 deaths had been recorded because of cluster bombs that failed to self-destruct, as they are meant to do, in Lebanon.

In order to keep the weapons in the British arsenal, the UK government is attempting to redefine the cluster bomb. The Ministry of Defence says a cluster bomb has to have 10 bomblets per rocket. The M73 has nine bomblets per rocket and falls outside the definition. Opponents say this new definition is extremely convenient. The M85 is defended because, in the MoD's words, it has an effective "self-deactivation device". However, as the experience of Lebanese civilians has shown, this often doesn't work.

The UK is also seeking an exemption for ballistic sensor fuzed munitions (BSFM). While certainly "smarter" than most "dumb" cluster bombs, BSFM pose serious risks. BSFM are comprised of two bomblets contained in an artillery shell. The bomblets are released from the shell and, in theory, are supposed to use heat sensors to locate the engines of tanks or personnel carriers. However, it could just as easily lock on to an ambulance or civilian car.

Many members of the public might think a British army general who earned the nickname "Rambo" in Northern Ireland may be gung-ho about keeping UK forces well-supplied with such lethal kit, but David Ramsbotham, now Lord Ramsbotham, is among the most scathing critics of cluster munitions. He points to an underlying failure in the government's argument that cluster bombs are of strategic importance.

If that's the case, he asks, why have UK forces never used the much-lauded M73? Many suspect it is because military commanders know that deploying the weaponry in Iraq or Afghanistan would be tantamount to tearing up the doctrine of winning hearts and minds, and branding British troops with the stain of civilian fatalities on a massive scale.

For Ramsbotham, there is no need for cluster munitions in the post-Cold War era. The weapons - first created by the Nazi regime - were seen as essential during the Cold War for holding back the Red Army if it tried to advance into western Europe.

Lord Ramsbotham is not alone. As many as 30 military top brass - as yet unnamed - from the rank of retired field marshal down to colonel are due to sign an open letter to the British government ahead of the Dublin negotiations, imploring ministers to vote for an outright ban on all cluster bombs.

Cluster bombs also seriously hamper post-conflict reconstruction. It's not an easy task for civilians to rebuild an area when there is unexploded ordnance scattered about. Ramsbotham says he can't understand why the UK government is pushing for exemptions. "What we need is more precision weapons, not indiscriminate ones," he added. Ramsbotham also sees Britain's last use of M85 cluster munitions - in Iraq in 2003 - as "inappropriate".

"These weapons are inefficient. They cover large areas with lethal bomblets that may not self-destruct and can remain a problem for years. What's worse is that they are attractive to children," Ramsbotham said. He believes that those in the military and the government who are pushing for the retention of cluster bombs are doing so simply because they don't like the idea of "losing something from the locker".

Ramsbotham also sits on the all-party group of cluster munitions. It is unanimous in its condemnation of the weapons and has expressed its concerns to the defence secretary, foreign secretary and the department of international development.

Simon Conway is, like Rams-botham, an ex-soldier. He retired a captain after tours of duty in Ulster and Germany with the Queens Own Highlanders. After leaving the military, he worked with the Halo Trust de-mining areas of Cambodia and Kosovo, and is now director of Landmine Action and a vociferous campaigner against cluster bombs. Like many campaigners, he was delighted when, in November 2007, Gordon Brown made a commitment to ban the munitions. His joy was short-lived.

He pours scorn on claims cluster munitions have a good record on self-destructing. Referring to the BL755 cluster munition, which the UK used in Kosovo and Iraq but has now withdrawn from service, Conway said claims that only 6% of bomblets failed to self-destruct were wildly inaccurate - in combat conditions, the figure was closer to 25%. During tests, weapons are thoroughly serviced and in prime condition before being fired over hard ground which all but guarantees detonation. In combat, they often land on soft ground, in tree tops or on roofs, where they remain undetonated.

"Our purpose is to stigmatise these weapons," he said. Conway claims Des Browne, the defence secretary, even admitted to him in private conversation the M73 was "not appropriate for counter-insurgency operations".

"If the government pushes for these exemptions, cluster bombs will just go on being used and the casualties will continue to go up as the weapons proliferate," he said. In fact, the weapons have already proliferated. Hezbollah, according to Conway, has obtained cluster weapons, and in 2000 a Halo Trust survey found cluster bombs had been dropped by Ethiopia on an Eritrean refugee camp; Eritrea also dropped Chilean cluster bombs on an Ethiopian school.

Although Britain is not alone in seeking exemptions - France, Germany, Japan and the Netherlands are also trying to keep some munitions inside the law - the vast majority of the developing world wants a ban. Laos is perhaps one of the keenest backers of a ban. It did, after all, experience the effects of 300 million cluster bombs falling within its borders 30 years ago. They still go on killing today.

Thomas Nash, co-ordinator of the Cluster Munitions Coalition, an umbrella organisation representing 250 humanitarian organisations in 70 countries, points out the BL755 cluster munition, now withdrawn by the UK, was exported from Britain to India and Pakistan, two countries in an almost perpetual state of cold war. The munitions also found their way into the hands of Serb forces during the Balkan wars.

The M85, he points out, has ribbons attached to it and can be mistaken by children for toys. Some 100,000 of these munitions were dropped around Basra by UK forces in 2003. A large number remained unexploded and led to deaths and injuries among civilians. Nash said Norway was one of the most courageous countries involved in the campaign to ban cluster bombs. Forty per cent of Norway's artillery is modified to use M85 cluster bombs, yet the country wants to see M85s banned. In effect, the decision means Norway is junking almost half its artillery capabilities.

"They are making the right decision," said Nash. "What we are seeing in Britain, however, is the UK seeking to promote its own narrow self-interest ahead of a shared interest in human security."

Judith Robertson, director of Oxfam Scotland, said Britain's push to exempt some cluster munitions would continue the "devastation of the lives of civilians". She warned that, where Britain leads, others would follow, and moves by the UK to keep cluster bombs in the military stockpile would lead to the weapons continuing to be produced and used. "We want an absolute ban," she Robertston said. "We must hold the government to account by reminding it of Gordon Brown's statements in the past."

Two men with first-hand experience of the horror weapons can bring to ordinary families are Mick North and David Grimason. Mick North's five-year-old daughter, Sophie, was killed at Dunblane in 1996; Grimason's two-year-old son, Alistair, was shot dead in a Turkish cafe in 2003. Both are calling on the government to honour its previous pledge to ban cluster weapons and not to go back on its word.

Grimason said: "In 2006, I met Des Browne to hand over the Control Arms petition calling for an international arms trade treaty. Mr Browne gave his support and since then the UK has championed the need for such a treaty. It thus seems very inconsistent to argue for loopholes to this specific treaty on cluster bombs, and I call on him to change his mind."

Mick North added: "As a father who lost his child to misuse of arms, I know the pain and grief caused. It is incumbent on the UK to do all it can to ensure more children don't die as a result of cluster bombs, and more parents aren't left grieving the loss of their innocent children. Loopholes or exceptions simply aren't acceptable. I really can't understand why the government should want to hinder progress of the process in Dublin."

An MoD spokesman said: "A ban on the use of all types of sub-munitions would adversely impact on the UK's operational effectiveness, impose serious capability gaps on our armed forces and take away one element of force protection; we cannot therefore exclude their use either in current or future operations The issue of definitions is seen as key to the successful conclusion of this process and that is why it is so important to ensure international consensus on this issue.

"The UK, along with many other nations, has tabled its own proposals concerning the types of cluster munition that might be prohibited. The UK's purpose is to negotiate a convention which balances the need to tackle humanitarian issues with the need to protect our men and women who are engaged in crisis management operations The UK supports a treaty that bans those cluster munitions that cause a post-conflict problem. Not all types of cluster munitions do this; as even some NGOs recognise."