Ban takes effect in six months

The most hated and despised weapons ever devised will be banned by international agreement next year.The last hurdle to a global, permanent ban on chemical weapons - poison gas and droplets which choke, poison blood or destroy the nervous system - has been passed with Hungary ratifying the international Chemical Weapons Convention (CWC). It will come into force on 29 April, after 28 years of negotiations.

Last night politicians, diplomats and arms control experts expressed delight. "This means CWC will definitely enter into force in six months' time," said David Davis, minister for Foreign and Commonwealth Affairs. "This is a milestone in international arms control efforts. The CWC is the first multilateral treaty to impose a complete ban on an entire class of weapons and a verification regime to monitor compliance."

Some 160 nations have signed the convention. Britain was the 51st, on 13 May this year. With Hungary, it has been ratified by 65, the number necessary to bring it into force.

The US and Russia, the only nations that have admitted still possessing chemical weapons, have not ratified the convention but as signatories they will be bound by it and will have to destroy all their remaining chemical weapons stocks. A review conference is to be held within 30 days of the convention coming into force and if the US and Russia want to attend they will have to have ratified it.

Iraq, which has made most use of chemical weapons in recent times, has not signed the convention but is regarded as a "special case", subject to surveillance by the UN Special Commission on Iraq.

The ban binds signatories to destroy production facilities and never to develop, produce, acquire or stockpile chemical weapons or transfer them to anyone, never to use chemical weapons and never to assist or encourage anyone to engage in any other activity prohibited by the convention, including the use of riot-control gases in warfare. Industrial, agricultural and pharmaceutical research, and research designed to enhance protection against chemical weapons, is still allowed.

Following their use in the First World War, the use of chemical weapons was banned by the 1925 Geneva Protocol. However, the right to use chemical weapons in retaliation was retained by many states, and the protocol did not stop the Italians using them in Abyssinia. Chemical weapons underwent further development in the Thirties, with Germany developing nerve gas. The threat remained during the Second World War and the Cold War. Negotiations on a treaty began in 1968 but progress was made only after a US-USSR agreement in 1990. This committed both to reducing their stocks to 5,000 tons by 2002. The remainder will now be destroyed.

"There isn't a political problem with that but the disposal of these substances will be expensive," said Anil Wahwa, spokesman for the Preparatory Commission of the Organisation for the Prohibition of Chemical Weapons in the Hague, set up under the convention.

A OPCW will now be set up, with a member from each of the signatory states, and an executive council of 41.