Ground level ozone gas, which is responsible for more than 1,500 deaths a year in the UK, is not being addressed by legislation and will only rise as climate change becomes more pronounced, according to a new report by the Royal Society.

Policies in the EU, Japan and the US have successfully reduced the occurrence of very high peaks of ozone, but ground-level ozone in the UK has increased by six per cent per decade since the 1980s as it is blown in from other parts of the world on weather systems.

More robust international regulations are needed to solve the problem, according to Professor David Fowler chair of the Royal Society's ground level ozone working group.

"Weather systems and jet streams transport ozone, and the pollutants that lead to its formation, often far from their point of origin," he said. "Here in the UK, for example, we receive most of our ozone from outside of Europe."

He added that until a globally co-ordinated approach is agreed on, "national and even regional level controls are unlikely to deliver the kind of reductions that are necessary to protect human health and the environment".

Ozone is formed when sunlight reacts with pollutants and naturally occurring chemicals in the air. The pollutants come mainly from vehicle exhaust fumes and the shipping sector, which has relatively poor emission regulations.

As well as affecting the respiratory system, ozone gas is also believed to have an adverse effect on food crops. Computer modelling studies have estimated that crop yields in India in the year 2000 were about 13 per cent lower for wheat, six per cent lower for rice and 19 per cent lower for soya beans as a result of the adverse effects of the gas.

Children, the elderly and asthmatics are particularly vulnerable, and a conservative estimate from the Royal Society claims that the annual UK death toll from the gas will rise 51 per cent to almost 2,400 people by 2020.

As well as being harmful in itself, ozone is considered to be the third most important greenhouse gas contributing to global warming.

"Ozone has become a global pollutant, with direct effects on human health, crop production, ecosystems and climate, yet control strategies are country or region based," said Professor Fowler. "A co-ordinated global strategy bringing ozone into international frameworks for controlling air pollutants and greenhouse gases is required."