Romano Prodi has welcomed the introduction of euro notes and coins as "tangible evidence that European integration is now irreversible".

Addressing the European parliament, the commission president said that the changeover had been both "a huge task and a huge success".

"Everyone who contributed to that success can feel proud," he told MEPs.

"The euro is becoming a key element in people's sense of shared European identity and common destiny. It is tangible evidence that European integration is now irreversible."

Following comments by Downing Street's former policy chief, David Miliband, that the new notes and coins will have "more effect than any words that politicians can come up with" in building the pro-euro case in the UK, Prodi takes the logic of the argument further with his view that the single currency mounts a compelling case for a united Europe.

"To millions of European citizens, the euro notes and coins in their pockets are a concrete sign of the great political undertaking of building a united Europe," the Brussels chief said. "As a symbol of that unity, the euro is having an even greater psychological impact than the abolition of passport controls at Europe's internal borders."