The articles are both politically and legally very awkward and have been the subject of some discussion in the Convention's steering committee, the presidium.

Recognising how emotive the issues are, the presidium has decided to leave the question on "retiring" from the Union open for discussion in the plenary.

It will just put forward the article in the current treaty but will suggest where the problems could lie.

Sources say that one of the burning questions will be how to negotiate the terms of a new agreement with the country that wants to leave the EU.

If the state refuses to accept the terms of the agreement that have been reached, this will put the Union in a very difficult legal position.

Cat among the pigeons

The other issue is ratification of the treaty and what happens to a country which rejects it in a referendum.

With the spectre of the Irish rejection of the Nice Treaty in the background, several EU members want to prevent a situation where they are held up from going forward by one state.

Convention president Valéry Giscard d'Estaing put the cat among the pigeons last year when he suggested that a state must ratify the treaty or be outside the Union.

There are several problems around this issue. First of all, how to get out of the current treaties.

According to international rules - The Vienna Convention on the Law of Treaties - all member states have to agree unanimously at a European Council to leave one treaty and enter the Union created by the Union.

If one country does not give its assent, then they simply cannot proceed with setting up a new Union with the new constitutional treaty.

The other problem is also ratification of the new Treaty. If Denmark – as a country that will put this to referendum – says no, what do other countries, who have already said yes, do?

"These problems are so difficult," said a presidium source. "We have discussed and discussed this issue."

The presidium will make public these and other articles next Friday.