A scientific team is carry out a one-year study into clams that servicemen were poisoned by chemical warfare tests at Porton Down, the Ministry of Defence (MoD) has announced.

The government-funded trial, which will begin in June, is to determine if there is enough evidence to justify a full study of veterans' claims that they were made ill by the tests.

The team will include scientists from Oxford University, the London School of Hygiene and Tropical Medicine and Imperial College, London.

The move comes after Wiltshire Police launched an investigation into the use of thousands of human guinea pigs at the top-secret establishment on Salisbury Plain.

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Campaigners say servicemen were subjected to experiments with nerve gas and other toxic chemicals after volunteering for what they thought was research into a cure for the common cold.

Veterans claim more than 20,000 servicemen were subjected to chemicals including mustard gas, nerve agents, CS gas and LSD at Porton Down - the bulk of them in the 1950s and 1960s.

About 800 have contacted the MoD to complain that their health had been affected.

But defence officials claim there is no evidence to back them.

Replying to a Commons written question from labour MP Nick Palmer, junior minister Lewis Moonie said: "The research will consist of a one-year pilot study.

"It will assess the incidence of mortality and cancer amongst a selected group of 500 Porton Down volunteers, compared with a control group of 500 other members of the armed forces."