Why does the European Union need a new treaty?

The rules and institutions of the EU need updating to take account of the accession of 12 countries since 2004, bringing membership to 27 nations. Under present arrangements, no more countries can join but several have applied, including Croatia, Macedonia and Turkey. Most countries believe that decision-making processes have become too cumbersome.

What happened to the EU Constitution?

The Constitution was agreed by EU leaders in 2004 as a way of modernising the EU but was rejected in referendums in France and the Netherlands in 2005. Tony Blair had promised a referendum but the British ratification process was put on hold, as it was in a further five countries, for a "period of reflection" which has culminated in this week's summit.

What is proposed in place of the Constitution?

The idea of a stand-alone Constitution, which replaces previous treaties, has been scrapped. Instead, the new document will be an 'amending treaty' that updates previous agreements, in line with British demands for it to look different to the failed Constitution so it does seem like the basis for a European super-state.

What remains from the Constitution?

Many of the elements of the Constitution will live on in the proposed new Reform Treaty, such as a full-time president of the European Council and an EU Foreign Minister, as well as fewer members for the European Commission and a change in national voting weights to reflect population levels. The German presidency of the EU, which is drafting the new treaty proposal, is also keen to include a shift to qualified-majority voting in an extra 51 areas of EU policy. It also wants to make the Charter of Fundamental Rights, a declaration made in 2000, legally binding.

What does Britain want?

Tony Blair has already secured his first goal - that the treaty is a traditional amending treaty rather than a constitution. The name constitution has also been dropped, as have references to the symbols and anthem of the EU.

But Mr Blair still wants to stop the Charter of Fundamental Rights from becoming legally binding, or at least to ensure that it does not apply to Britain's social and labour laws. He also wants to retain the British veto over justice and home affairs decisions and is likely to opt out of any move to qualified majority voting. Mr Blair also wants limits on the power of the proposed EU Foreign Minister.

What happens next?

EU leaders are preparing for a long haul summit, possibly lasting well into Saturday. The treaty will not be written this week but Angela Merkel, the German Chancellor, wants unanimous agreement on a "mandate", or detailed official framework, for an Inter-Governmental Conference (IGC) before Germany's presidency finishes on July 1. An IGC is the formal body which includes representatives from each country and which will write the treaty. The plan is for the IGC to finish by November, in time for a signing ceremony in December, followed by a fresh round of ratification expected to take a further 12 to 18 months.

Will there be a referendum in Britain?

Gordon Brown is keen to avoid a referendum because it would take up a lot of time and energy during the first crucial months of his premiership, and cloud the run-up to the next general election. He will hope that Mr Blair gets a deal from the summit that means he can fend off calls for a referendum by arguing that the treaty is no longer constitutional in character, nor does it transfer power to Brussels. He is not alone in wanting to avoid a referendum - it is also the goal of the the French and Dutch, whose leaders will similarly argue for parliamentary ratification on the grounds that the EU has backed away from an unpopular Constitution.

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