At the insistence of the Portuguese EU presidency, all 27 EU leaders and their delegations will fly to Lisbon on 13 December for a special signing ceremony of the bloc's new treaty – and then jet on to Brussels for a regular EU summit meeting the next day.

The cumbersome travel arrangements allow Portugal to call the new treaty the 'Lisbon Treaty' – but they have also led to criticism that EU leaders are setting a bad example by preaching about green values but then unnecessarily contributing to global warming through the short round trip.

To reduce at least part of the summit's carbon footprint, the Benelux leaders will board a Dutch government airplane when flying to and from Lisbon – something suggested by Mr Balkenende.

The Dutch plane is likely to depart from The Hague and then pick up Mr Verhofstadt and Mr Juncker in Brussels before flying on to Lisbon.

"The goal of this initiative is to give a good example in the current times of climate- consciousness," said the Dutch spokesman adding that it is up to other leaders "to decide for themselves" whether they would like to follow the example.

The Benelux' eco-move is likely to spark renewed attention to the EU summit's carbon footprint – taking place just after a high-level meeting on climate change in Bali (3-14 December) where the EU will seek to convince international partners to follow its binding carbon-reduction targets.

Meanwhile, it seems unclear whether other EU leaders can easily follow the example of the Benelux trio – who have the advantage of living near Brussels, making it easier to depart and return on the same plane.

In addition, outgoing Belgian prime minister Verhofstadt is seen to have contributed to the travel fiasco by resisting a Portuguese suggestion to hold the whole December meeting - including the regular EU summit - in Lisbon.

Diplomats said Mr Verhofstadt refused to set a "precedent" of holding the summit somewhere else than in Brussels.

At a late-night summit in Nice in 1999, the Belgian leader fought hard to have all future summits held in the Belgian capital.