The European Court of Justice (ECJ) has ruled that the European Parliament must continue to hold 12 sessions a year in France, despite its usual location in Brussels, at a cost of about €200m a year – and the huge environmental damage caused by fleets of lorries transporting people, documents and equipment hundreds of miles, and back, once a month.

The case was brought before the ECJ after MEPs adopted two amendments to parliament’s calendar of plenary sessions for 2012 and 2013, scrapping one of the two sessions planned for October and merging the two into one week-long session.

The move by MEPs sought to save money from the EU budget, and reduce the European Parliament’s environmental impact and, crucially, to assert their right to choose their own place of operation.

The ruling brings into focus the need for parliament to resolve the situation quickly – and the need for treaty change to bring an end to what has been dubbed ‘The EU’s Travelling Circus’.

London’s Green MEP Jean Lambert said: “The ECJ ruling was expected – but it brings into sharp relief the need for EU treaty change to end the wasteful ‘travelling circus’ once and for all.”

Keith Taylor, Green MEP for South-east England, added: “The Greens in the European Parliament have long campaigned against the ecological absurdity of having two seats.  By operating in one place, the Parliament would not only save money that could be invested in the environment but would also dramatically reduce emissions – something all public institutions should be doing.

In 2007, Jean and her Green colleague Caroline Lucas commissioned the paper ‘European Parliament two seat operation: Environmental costs, transport and energy’, which revealed that the split site arrangement produced an extra 20,000 tonnes of carbon dioxide every year – more than some countries.