"There are clearly a number of reasons for it, some of which include the British weather and people wanting to get away from that, some of which are to do with our being an island," said spokesman Geoff Wicken.

"But the rapid growth in low-cost flying has undoubtedly been a factor," he told Reuters.

The British government has pledged to cut the country's carbon emissions as part of the battle against global warming, but it is also backing rapid expansion of air travel.

It has come under relentless pressure from climate campaigners to curb airport expansion and has called for flights to be included in the European Union's Emissions Trading Scheme.

Scientists say carbon emissions from flights are at least twice as harmful to the environment as those at sea level.

However, the road carbon emissions of Britons at 2.4 tonnes per adult are less than one third of Americans' 7.5 tonnes.

In fact overall American adults have the biggest annual travel carbon footprint in the world at 7.8 tonnes, more than double France's 3.7 tonnes, which comes in at number two.

Third on the list at 3.1 tonnes is Britain, followed by Ireland on 3.0, Germany on 2.4 and Spain on 2.2 tonnes.

India is at the foot of the table with an annual travel footprint of just 200 kg per adult, with second-to-bottom China on 500 kg. But TGI warned that travel emissions in those two booming economies were rising rapidly.

It also pointed out that its figures were calculated per adult, meaning it did not provide overall travel emission details of each country. That would be achieved by multiplying the figures by the adult population.