The prime minister has defended his decision to hold a referendum on the EU constitution.

Writing in Le Monde newspaper on Wednesday, Tony Blair argued that it held the chance for both pro-Europeans and Euro-sceptics to put their views to the British people.

His article is expected to add pressure to French president Jacques Chirac, who has so far refused to hold a similar vote.

"It is impossible to argue intelligently when the debate centres not on the merits of the planned constitution, but on whether there is good reason to consult the people on the subject," Blair said.

Apology

He added that he was sorry the issue had been presented "in such a bad light".

Meanwhile, European parliament president Pat Cox called on British politicians to "get on your bike" and start campaigning in favour of the constitution.

"When I look at the state of the public opinion polls and a large number of the euro myths that seem to abound, I recall Norman Tebbit's phrase 'get on your bike'," he told the BBC Radio 4 Today programme.

"It is not a time to hang about. Even if it is in a year, 18 months, whenever it could be, it takes a considerable period to get some basic messages across to the broad mass of the public."

The referendum offers a "generational defining moment in Britain", he argued.

"Is Britain up for it? To give real leadership and play a central role in Europe? Or is Britain opting out? And frankly, it will boil down to that basic instinct in the end," he said.

Enlargement

In his article, Tony Blair insisted that the accession of 10 new countries at the end of the week would accelerate changes to the European Union.

"By their experience and determination they will breathe a new energy into the European Union and step up the pace of modernisation for the great benefit of all," he wrote.

"It will give the EU additional weight if we have the political will to exert it."

He went further, predicting that Bulgaria and Romania will also be able to join the EU within the next two to three years, while claiming that countries including Croatia and Turkey are "on the right path".

"As soon as Turkey fulfils its criteria for accession, it will bring a new dimension to the EU, providing a bridge with the Islamic world," he argued.

However, new French foreign minister Michel Barnier insisted that under current circumstances, France would veto any membership bid from Turkey.