PATRIOTIC drivers who attach flags to their cars during World Cup fever will pay an extra pound an hour in fuel costs, an academic worked out.

Attaching two flags to the windows of a medium-size car causes it to burn an extra litre of fuel an hour, travelling at an average of 30mph, according to Dr Antonio Filippone.

He also calculated that if half a million motorists choose to attach flags to their cars it will cause an extra 2.8m kilos of carbon dioxide to be released into the atmosphere.

The extra fuel consumption is caused by the flags creating drag on the cars.

Dr Filippone, of the University of Manchester's School of Mechanical, Aerospace and Civil Engineering, carried out the research for a paper entitled What Is The Fuel Wastage From The Flag On Your Vehicle?

He said: "The extra drag which is generated by these flags can reduce a car's fuel economy by up to three per cent during a one-hour journey.

"This may not seem significant to the individual but if half a million cars are flying these flags it means that we could see up to 1.22m litres of extra fuel burned during the World Cup by those with flags."