Two years after the European Union constitution was rejected by French and Dutch voters, a replacement treaty has now been negotiated.
Originally called the Reform Treaty, it has now been re-named the Lisbon Treaty.
Here Ruth Lea, director of the Global Vision think tank, and Charles Grant, director, of the Centre for European Reform go head to head.
RUTH LEA - GLOBAL VISION
It is now clear that Reform Treaty is in all but name the Constitutional Treaty. It is a treaty of supreme significance.
When the new treaty is enforced, assuming that it will be, the EU will have all the powers to complete a true European political and economic union. And the road to European integration, which started back in the early 1950s with the European Coal and Steel Community, will be all but complete.
It cannot be emphasised too strongly that, however significant the previous EU treaties were, the Reform Treaty is unique. Once enforced, there will quite simply be no more significant powers left solely with the governments of the member states, and outside the orbit of the EU's formal institutions.
Of course, member states may still pursue their individual foreign and defence policies, for example, but their activities will be increasingly circumscribed by the EU and their national sovereignty diminished.
For the UK... increasing political and economic integration can only be to its disadvantage
And is the Reform Treaty good for Europe, on the one hand, or good for the UK, on the other? Concerning the other EU member states, it is for them to make their choice. If European integration is their ambition, then the treaty is right for them.
But for the UK, with its unique global links and lack of sympathy with the highly regulated and protectionist EU model, increasing political and economic integration can only be to its disadvantage in the rapidly changing world of the 21st Century.
CHARLES GRANT - CENTRE FOR EUROPEAN REFORM
The Reform Treaty is good for both Europe and Britain, in three ways.
First, if the treaty had been blocked, Europe's governments would have had to spend longer discussing treaties and institutions, instead of real issues in the real world. But with the treaty out of the way, Europe's leaders will be free to focus on big challenges like energy security, international terrorism, climate change, illegal immigration, Russian authoritarianism and the Middle East.
A middle-sized country like Britain cannot tackle such issues alone. It needs to co-operate with partners that share similar interests, and the EU provides a suitable forum.
Second, the Reform Treaty allows the EU to keep open the possibility of taking in more members. Without the new treaty, many governments would have blocked further enlargement, on the grounds that the EU will become incapable of effective decision-making if it goes on expanding without strengthening its institutions. Britain has rightly championed enlargement, as a means of spreading democracy, security and prosperity across the continent.
The external representation of the EU is currently a mess
Third, the external representation of the EU is currently a mess. The country with the rotating presidency, the commissioner for external relations, and the 'High Representative' (currently Javier Solana) each tries to represent the EU, leading to confusion and mixed messages.
The Reform Treaty establishes a new system: a single High Representative will speak for the EU to the outside world. But decisions in foreign policy (as with defence policy, taxation and the EU budget) will still require unanimity, which means that Britain - or another country - can block any policy it dislikes.