A smog warning was issued in Brighton and Hove today just days after the city was named one of the UK's most polluted places.

People with respiratory problems were urged to take precautions as ozone levels rose across the South-East.

The air pollution is expected to last until the weather begins to cool on Saturday.

The Department for Environment, Food and Rural Affairs (Defra) issued the warning for London, the South-East, East Anglia and central England.

Asthma sufferers are advised to keep their inhalers with them at all times.

Ozone, caused when vehicle emissions react with sunlight on windless days, combines with other chemicals and can trigger coughing fits, shortness of breath and sore throats.

It can even be fatal. Up to 800 deaths in the UK were attributed to poor air quality during a heatwave in 2003.

Figures released by the Chartered Society of Physiotherapy on Tuesday showed Brighton and Hove to be the ninth most polluted place in Britain.

Last July the city was earmarked as an Air Quality Management Area and the council was given an 18-month target to come up with a strategy for reducing pollution.

The city suffered exactly the same problem last August when the safety limit for summer smog was passed every day of a nine-day heatwave.

Background levels of ozone at the Foredown monitoring station, Hove, exceeded 120 parts per billion twice during that time. The Government's target to protect health is 50 parts per billion.

Nigel Jenkins, project development officer for the Sussex Air Quality steering group, said : "I think we should be concerned because ozone is a gaseous pollutant so it can affect everyone.

"Asthmatics and people with heart conditions should be careful about how much activity they are doing." Chris Todd, of Brighton, Hove Mid-Sussex Friends of the Earth, said: "We have seen high levels in Brighton and Hove mainly from transport pollution because we don't have any heavy industry.

"Quite simply the Government and local authorities have to get to grips with this poison in our air which is literally killing us."

Defra is asking drivers to avoid using their cars where possible to help reduce pollution.

If they must drive, they should switch off the engine if they expect to be stationary for more than a couple of minutes.

They should also avoid spilling petrol as this will evaporate and release toxic hydrocarbons.