EU: The EU constitution debate explained.
Why is the constitution needed? Because the European Union is bigger and more complex. It has 25 members from Cyprus to Lithuania, with more on the way. That makes it essential to have a set of rules to make sorting out disputes possible - and at the moment the Union is guided by a series of complex treaties dating back to 1957. The constitution also sets out the values on which the EU is based and simplifies the provisions of existing treaties.
Who wrote it? The idea for a new constitution came from France and Germany. It was drawn up by a constitutional convention headed by the former French president Valéry Giscard d'Estaing and completed by European leaders in 2004.
So what does it change? The most important change is to widen the number of subjects on which the EU can take decisions without requiring the agreement of every member state. It creates a new double majority system of voting, involving a requirement of 65 per cent of population and 55 per cent of member states for a majority. Supporters say that this change is essential now that the EU has so many members. Critics argue it either gives too much, or too little, strength to nation states. The constitution also clarifies the EU's powers and legal status. It simplifies some of its structures and raises the possibility of some new ones and creates a European foreign minister and new presidency. The constitution also goes further than past EU treaties in defining the rights given to EU citizens. What does it not change? Fundamentally, it makes no big changes to the way the EU has worked up to now. The European Commission, Parliament and Council of Ministers will continue in more or less their current form. Where ministers cede veto powers, however, MEPs win the right to more of a say.
So what are the objections? They vary. In France some critics dislike the constitution because they say it gives too much power to nation states and emphasises the free market, while others believe it takes too much power away from the nation.
In Britain critics oppose the idea of an EU constitution - as opposed to a new treaty - arguing that it suggests the EU, rather than its members, now has the upper hand. Many also oppose the loss of the right to veto policy in 26 extra areas. There is also concern about the possibility of EU intrusion into areas such as taxation and foreign policy.
In Ireland, criticism is largely focused on the reduction of veto rights, a shift in the voting balance towards larger states (although small states still remain proportionately over-represented), the loss of an automatic right to a commissioner all the time, and the consolidation of the military dimension of the Union.
What happens if the constitution is rejected? The European Union will continue to rely on the current rules, drawn up in the 2001 Nice Treaty. But almost everyone agrees some sort of new deal will be needed in the end.