Nuclear weapons are the only Weapons of Mass Destruction not yet explicitly banned under international law. A clear majority of countries has recently pledged to end this unacceptable anomaly, and a new UN working group is meeting this year in Geneva "to address the effective legal measures, provisions and norms that will be needed to attain and maintain a world without nuclear weapons".

They aim to ban the ownership, deployment, stockpiling, storage or transport of nuclear weapons under any circumstances: this would apply to all countries equally. This is ultimately the only way to prevent the dangers of accidental or terrorist-driven nuclear hazards.

The UK is one of a small minority of countries that have opted out of these talks - despite saying repeatedly that they want to play a leading role in multilateral disarmament. But if a new ban is enacted, renewal of Britain's Trident system will unquestionably be illegal, whether or not Britain attends.

We call on the British government to drop its opposition to the UN mandated 'Open Ended Working Group' (OEWG) and to take an active and constructive part when talks resume in May 2016. In parallel, we call on Britain's government to delay any decision on the replacement of Trident until those talks have taken place.

And we call on Britain's other party leaders also to attend the UN Working Party, to bring its work to the attention of the British public and parliament, and to take account of its conclusions if or when the vote on Trident takes place.

More information from International Campaign to Abolish Nuclear Weapons at http://www.icanw.org/