A new ruling by the UK Government that depleted uranium (DU) weapons are acceptable under international humanitarian law may be challenged in court by campaigners angry that ministers are clinging to a "toxic Cold War relic".

The ruling means that DU tank shells could again be tested at the Dundrennan military firing range near Kirkcudbright on the Solway coast. Past tests, which have contaminated the site, have brought cross-party condemnation from Scottish politicians.

DU is a radioactive and chemically toxic heavy metal produced as waste by the nuclear industry. It has been widely used by UK and US military forces to harden armour-piercing shells fired in the Gulf, Balkans and Iraq wars.

When DU weapons burn, they release a hazardous dust that can contaminate wide areas. Civilians and soldiers exposed to the contamination claim to have suffered from cancers, birth defects and other illnesses as a result.

A review of the legality and dangers of DU weapons under the Geneva Convention was launched last November by the UK Armed Forces Minister, Liberal Democrat Nick Harvey. This came after he was forced to apologise for misleading MPs by saying that the weapons had already been cleared by such a review, when in fact they hadn't.

According to Harvey, the review has concluded that DU shells are "capable of being used lawfully by UK armed forces in an international armed conflict". They do not cause "unnecessary suffering", or pose a "significant risk" to public health or the environment, he said.

But this has been fiercely disputed by the Campaign Against Depleted Uranium (CADU), which is now seeking legal advice with a view to taking the Government to court. The group said Harvey has downplayed the risks of DU, and misinterpreted the Geneva Convention.

Aneaka Kellay, of CADU, said: "It is disturbing that the Ministry of Defence appears to have ignored the findings of international organisations such as the UN Environment Programme, overlooked the wider conclusions of the World Health Organisation's reports, and ignored the widely accepted potential risks the chemical toxicity of DU poses.

"This latest Government decision has again failed to take into account the potential risks of DU weapons testing and use. The Government must come clean, recognise DU's unacceptability and remove this toxic Cold War relic from its arsenal."

Kellay demanded that the MoD release a copy of the DU review, which has been kept secret. She said: "Their apparent cherry picking of the facts suggests a lack of transparency in the review system."

Katy Clark, the Labour MP for North Ayrshire and Arran, also called for the review to be published, saying: "The ministerial statement made by Nick Harvey is not enough to regain public trust in the MoD."

She also said that there were "serious doubts about the accountability and transparency of the MoD" because it had misled the public for years about the DU review.

"Depleted uranium is an issue of serious public interest, and only an open and democratic discussion into its use and legality under international humanitarian law will be acceptable."

The UK Government ratified additional protocol 1 of the Geneva Convention in 1998. Article 36 of that requires that weapons are subject to a legal review to assess whether they are "capable of being used discriminately", or cause "widespread and severe damage to the natural environment".

The MoD argued that UK DU munitions, known as Charm-3 and fired by Challenger tanks, did not breach these provisions.

Harvey said: "The available scientific evidence continues to support the view held by the UK that such munitions can be retained for the limited role envisaged for their employment.

"Given the challenging situations in which we expect our service personnel to operate, it would be wrong to deny them legitimate and effective capabilities that can help them achieve their objectives as quickly and as safely as possible."

The dirty dozen: Scottish sites contaminated by radioactivity

A dozen sites across Scotland suspected of being contaminated by radioactive waste from past military or industrial activities have been named by the Scottish Environment Protection Agency (Sepa).

One is the Ministry of Defence firing range at Dundrennan on the Solway Firth, where depleted uranium tanks shells have been tested.

Others include former air force, army and naval bases around the country where radium used to make dials glow in the dark has been dumped, as at Dalgety Bay in Fife (pictured, left).

There are also former radium factories in Wishaw and Balloch, as well as beaches contaminated by the Dounreay nuclear plant in Caithness. There have been reports about the sites before, but this is the first time that Sepa has identified them all as potentially contaminated.

Sepa had been insisting on keeping the list of sites secret for fear of causing "unnecessary alarm or distress to local residents". But it has now released it following appeals under freedom of information legislation.

The list was compiled to help determine whether "further work is needed" to protect the public, according to Sepa's radioactivity specialist, Paul Dale. Some historic activities "may have resulted in the presence of radioactive contamination which needs to be assessed," he said.

He added: "To date the only site where further actions have been required has been Dalgety Bay."

There, the public has been barred from a section of the foreshore since last October and the harvesting of shellfish has been prohibited since May.