Around 200 South Hook LNG workers are threatening industrial action over health fears at the site.

Since the beginning of December 2005, workers employed by Chicago Bridge Iron have complained about poor ventilation in the LNG tanks.

In each tank the men work alongside diesel-fuelled equipment.

The workers are claiming that they are experiencing throat and chest problems after breathing in the diesel emissions.

Douglas Corbett a GMB Union shop steward said: "It has been three months and now we are having to threaten industrial action before anything is done."

One worker, who did not wish to be named, speaking from a mobile phone from inside one of the tanks said: "At last they are doing health and safety checks. No-one is working in Tank One but in here (Tank Two) we have got 12 to 14 welders going, cranes, forklift trucks and cherry pickers running to test the fumes. The air is blue. The ventilation is not adequate.

This is going to kill us if nothing is done."

Mr Corbett continued: "These men are breathing in vast amounts of carcinogenic emissions in an enclosed space with poor ventilation. In an eight to nine hour shift it becomes unbearable. This is a very unhappy workforce."

A spokesman from South Hook LNG said: "Concerns have been expressed by personnel over air quality in the tanks. An independent company, Anchem, has tested air quality and found it acceptable. This afternoon (Monday) all the welders have been moved into Tank Two in order to test air quality under high workload conditions.

"The safety of our workforce is of paramount importance to South Hook and we will continue to monitor the situation."