By Chris Morris BBC Europe correspondent in Brussels

When the EU's Convention on the Future of Europe began its work last year, there were suspicions that the public debate was just for show.

National leaders, it was argued, would make the real decisions behind closed doors.

Not any more.

Now the Convention is stacked full of foreign ministers and senior members of national governments.

Everyone takes it seriously, and its most important phase is about to begin.

Paving the way

Within six months, it is expected to present a draft constitution, setting the tone for the way Europe functions for the next generation.

Ten more countries are due to join the EU

The Convention meets for two days in Brussels this week to discuss institutional reform.

What that really means is a debate about power within the EU, and who holds it. The 105 members of the convention will examine a plan put forward last week by France and Germany to reform the Union by giving it two presidents - one at the European Commission, the EU's executive arm, and one at the European Council, which brings together the leaders of individual member states.

Expansion fears

Like many others, France and Germany believe the current system, where each EU member state is in charge for six months, won't work when the union expands next year to include 25 countries in all.

D'Estaing says the European Council must reform

Instead they want a permanent President of the European Council to represent the EU around the world.

They have also called for the President of the European Commission to be elected by the European Parliament, giving the post greater democratic legitimacy.

It is part of an effort to balance the demands of countries like Britain and Spain who want to increase the power of nation states within the union, and smaller countries which want to strengthen the Commission, and its central authority.

France and Germany were split between the two camps themselves, and this is their suggested compromise.

Opinion divided

Some say the Franco-German plan is a recipe for chaos.

But the chairman of the Convention, Valery Giscard d'Estaing, argues that it is an improvement on the current system.

"I believe it can work", he says. "At the moment, the president of the Council is a rotating president, and the rotation will now take 12-and-a-half years. Is this sensible? No."

Where France and Germany lead, the rest of the EU tends to follow, but this is not yet a done deal.

Misgivings

It has already been criticised by the European Commission itself, and by several national leaders.

They all fear that the proposed new president of the Council would diminish the traditional authority of the Commission, allowing big countries to run the show themselves.

"There are a lot of countries which have misgivings about having two presidents", said Jacki Davis, the editor of E!Sharp magazine, "whether it will work, and whether their interests will be protected. So there is going to be a real struggle".

The Convention has plenty of other issues to discuss: notably how to make better connections between the EU and its citizens.

But priority one is to decide who is in charge.

Expect debate to be heated, as member states lobby to defend their own vision of the new Europe.