Builds on the status quo with reforms to make the EU work better. Drawn up after more than two-and-a-half years under the chairmanship of the former French president Valéry Giscard d'Estaing, it is the result of compromises and trade-offs. It combines existing treaties into one text and changes EU decision-making structures to help an enlarged EU operate more efficiently. It creates a new president of the European Council and an EU foreign minister. Other changes include a voting system linked to population size and a cut in the size of the Commission from 2014. Nine countries have already ratified the treaty.
NATIONS IN FAVOUR: Spain, Italy, Greece
The British model under which European co-operation is limited or kept at an inter-governmental level (preferably with national vetoes). The cornerstone is seen as the single market, allowing free movement of goods and eliminating trade barriers. Meanwhile, the UK has always favoured EU enlargement in part to weaken prospects for closer integration in core economic areas such as harmonising taxes. Britain has won new allies with the accession of Eastern European nations which tend to be more Atlanticist in instinct and put greater onus on free markets and competition than social protection.
NATIONS IN FAVOUR: UK, Poland, Estonia
United States of Europe
The dream of some of the EU's founders such as Jean Monnet and Altiero Spinelli, the idea of a federal Europe has receded as the EU has enlarged. It describes a division of responsibilities between a central authority and states, regions or provinces. But it is usually coupled with the term "superstate" in Britain, or shorthand for closer European integration, for example on the economy, taxation, agriculture and the environment. Founding EU nations (France, Germany, Italy and the Benelux countries) traditionally supported closer union, though even in these, its appeal fades.
NATIONS IN FAVOUR: Luxembourg, Belgium
An idea debated much over the past decade which would allow an inner core of countries - probably based on France, Germany and the Benelux - to forge ahead with closer integration, leaving Britain and others in the slow lane. It already exists with the single currency and the Schengen passport-free zone. The Nice Treaty allows groups of nations to identify areas where they want to co-operate more, though this has never been put into effect. If France and Germany could agree on common objectives they might use the mechanism, for example, to boost economic co-operation in the eurozone.
NATIONS IN FAVOUR: France, Germany