The Green Party has called on the National Assembly to press for an independent health study of a former chemical weapons factory in north Wales.

Members fear contamination of the site in Flintshire may be the cause of continuing high levels of cancer.

During World War II the Valley Works at Rhydymwyn, near Mold, produced hundreds of tons of mustard gas and also helped to develop the technology used in the first atomic weapons.

The site is presently not in use and closed to the public.

Secret history

The War Ministry first took advantage of the numerous lead mines in the area in the late 1930's to establish an underground storage facility for TNT explosives.

It was fear of a Nazi chemical weapons programme that later led to the development of British weapons of mass destruction.

Bombs and shells were filled with chemical agents and stored in the bunkers beneath the north Wales countryside until the early 1950s.

The Valley Works remained one of the most secret British military installations during the Cold War and was a source of local rumour and speculation.

It was even claimed that the Royal family would use the caverns underneath Rhydymwyn as a refuge from a Soviet nuclear attack.

Make safe

The Ministry of Agriculture, Fisheries and Food now controls the derelict site.

Experts employed by MAFF tested the area around the Valley Works for toxic contamination in 1998 after pressure from local people.

Soil and groundwater samples were taken by scientists and analysed in a laboratory.

The Government said it planned to spend millions of pounds to make the land safe for public use.

Flintshire County Councillor Klaus Armstrong Braun, a Green Party member, said he did not believe that the plan went far enough.

MAFF insists there is no risk to people living in the Flintshire area from any toxic residues buried underground.