Two senior economists have predicted economic tribulation following a 'no' vote. The euro could be undermined leading to raised interest rates in the new member states and possibly in the euro-zone, too. More seriously the European Union would look pretty silly in the eyes of the rest of the world. The egg on our faces might prove that we were human and democratic, but the Union's credibility would suffer, especially among emerging regional groups in Asia, Africa and Latin America, keen to follow the European model.

This apart, the short answer is nothing very much - or at least not immediately. Our operational basis is currently the 2000 Nice Treaty; this will continue for another couple of years whatever happens. Only later will the effects begin to be felt. One official talked this week about a gradual seizing up of the Union's decision taking machinery - the difficulty of operating on a unanimous basis in many areas with 25 member states.

Expect, too, the same complaints about lack of transparency, of democratic deficit, of imbalance between large and small states, of vagueness about responsibilities, that were recognised as lacunae in the Nice Treaty and which kick-started the Constitutional project five years ago. The status quo may be an option; but it is a very poor option.

No 'Plan B'

And yet there is no 'Plan B' to be trotted out if the Constitutional treaty is not ratified. No one knows quite what would happen in the event the French vote 'no'. Margot Wallström, the Swedish Commissioner responsible for communications, will only say that member states would meet in the European Council to consider what to do.

One might have thought it more use for the European Council to meet before an indicated 'no' vote, rather than after it, on the basis that keeping the ship afloat was more useful than a salvage operation.

Given the positive endorsement of the Constitution reported in opinion polls a year ago in all countries other than Britain, ratification was taken as a 'fait accompli.' Not so any more. The Constitution has been losing public support almost ever since. And not just in France, where once the polls showed a 60:40 split in favour, but right across the Union. It is worth asking why.

The major part of the Constitution is technical - a tidying up of existing treaties in the interests of transparency and simplicity. The public has little interest in such detail, the scrutiny of which we pay our parliamentarians good money for.

Then comes the Charter of Fundamental Rights. That is important, but the rights are only those we demand. This, too, is surely something for Parliamentarians.

That leaves only 30 pages (out of 482) that are properly constitutional. Even these consist largely either of matters that we thought were already the case - eg that any European state can potentially join the Union - or measures that we might expect - eg that the Council of Ministers should meet in public. Nor do the technical measures, the size of Parliament, Commission, votes in the Council, have much resonance with voters either.

We are not nation-building

In the light of previous advances in the European construction - the Single Market, the euro, Enlargement, open borders and so on, the public can legitimately ask 'where's the beef?' For after 20 years all that the Treaty may be remembered for is the creation of a Foreign Minister. And even this exists already in good measure.

The fact is the Constitution, with its portentous appellation, has been desperately oversold. Right from the time an ageing French President with his eye on history decided to produce a document that he hoped would last for 50 years in a Convention that recalled both French and American Revolutions.

We are, however, not nation building. The reality is that the Constitution is a largely technical measure needed to ensure the continued smooth functioning of the Union. It is a well constructed and very necessary framework, but inside is little that wasn't there before. When people learn this they lose enthusiasm - worse, on the principle of nature and vacuums, they fill up the framework with their own skeletons and prejudices. In vain does President Chirac plead that the Constitution has nothing to do with Turkey or with liberalising the Services market.

It is not too late to make a fresh presentation. The European Council should meet now and then embark on a Council led campaign. Leaders from all over Europe need to tell French voters that their referendum is not just a French affair but a European affair taking place in France. If that looks like a European travelling circus, so be it. European leaders, collectively, need to talk to European citizens, collectively, explaining what the partnership and this treaty is all about.

This campaign should not sell the Constitution as something historic; this is not about European liberty leading the people. The message should be that the great steps in peace and prosperity that have been achieved in Europe have been achieved by member states working together. The Constitution will help them to continue to do that, preserving the advantages that have been gained. It is a vital technical measure that Europe needs desperately if it is to function properly and deliver what its member states want it to do and what much of the world, mired as it is in poverty and crisis, has a right to expect.

The author is editor of EuropaWorld