However, a study published Wednesday by Green members of the parliament said that the assembly's monthly trek between its two headquarters in Brussels and Strasbourg produces the equivalent of 20,000 tonnes of carbon dioxide (CO2) emissions.

"We already know that the EP's multiple seat arrangement costs the EU taxpayer more than 200 million euros a year, now we have concrete evidence of the damage caused to the climate by the travelling circus," said Green MEP Caroline Lucas.

"At least 20,000 excess tonnes of CO2 are belched into the atmosphere each year: the equivalent of 13,000 return flights from London to New York," she added.

The parliament meets for four days every month in Strasbourg and the rest of the time in Brussels, forcing thousands of EU lawmakers, interpreters, other staff and journalists to make a monthly pilgrimage to the Alsatian capital.

The study, conducted by University of York Professor John Whitelegg, said the monthly shuffle generated "a very minimum" of 18,900 tonnes of CO gases although actual emission were likely to be closer to 30,000.

Keeping the parliament's activities in Brussels permanently would cut 3,900 tonnes of CO2 emissions in electricity and gas alone, it said.

While the monthly trip to Strasbourg is unpopular with many lawmakers, other officials and journalists, there is little chance the arrangement will be changed.

That would require the unanimous agreement of member states, and France for one, is keen to keep the parliament -- seen as a prestige symbol -- in Strasbourg, if only for four days a month.