A surge in outdoor heater use in pubs and cafes could cause Hounslow's carbon emissions to soar after the smoking ban comes into force on Sunday, 1 July, Darren Johnson, a Green Party member of the London Assembly, has warned Across London, the increased use of patio heaters could generate more than 20,000 additional tonnes of carbon dioxide.

Mr Johnson said: "Outdoor heaters are an extraordinary waste of energy and carbon emissions. They do more to heat the climate than they do for people.

"Each patio heater generates 2.2 tonnes of carbon dioxide on average per year - the equivalent to driving a car for more than 6,000 miles."

He added: "For the sake of the climate, I urge pub and café owners to kick the patio heater habit."

After smoking bans were introduced in Dublin, New York and Toronto, sales of outdoor heaters increased dramatically.

Scotland became the first part of the UK to introduce a smoking ban in enclosed public places. It is estimated that half of all pubs in Scotland bought at least one patio heater after the ban came into force in March 2006.

Mr Johnson said: "There are 5,240 pubs and bars in London, and 12,995 restaurants and cafes.

"If half of these businesses installed just one outdoor heater, this would generate over 20,000 tonnes of carbon dioxide.

"In some European cities including Copenhagen, outdoor cafes and bars give customers blankets rather than patio heaters".