Negotiations seeking agreement on the draft European Constitution began with an Inter Governmental Conference (IGC) in October 2003 and were completed in June 2004, during Ireland's EU Presidency, when all elements of the proposed European Constitution were agreed. The European Constitution sought to consolidate all previous treaties in a single text and to make significant changes. The European Constitution could only come into effect if and when ratified by all Member States. In 2005 the people of France and the Netherlands voted against the European Constitution. In both countries debate had been intensive and voter turnout was high. While voters were prepared to support an economic union, they opposed to the creation of a new European Union.

In response, the European Council called for a 'period of reflection', during which a broad debate would take place in each Member State, involving citizens, civil society, social partners, national Parliaments and political parties. In March 2007, the European Council met in Berlin and adopted a Declaration on the 50th Anniversary of the Treaty of Rome, which laid the foundation for today's EU. In the Declaration, the leaders of Europe were 'united in our aim of placing the European Union on a renewed common basis before the European Parliament elections in 2009'. The German Presidency presented a report to the European Council in June 2007 based on extensive consultations with Member States about the future of Europe. The European Council agreed a detailed mandate for an IGC to prepare a new Treaty: The Lisbon Treaty. The IGC mandate provided that the new Treaty would be based upon the existing Treaties and it would not have 'constitutional characteristics'. This meant that the title 'Constitution' was no longer used and would no longer appear in the text of the amended treaties. However, the legal effect would be to implement indirectly rather than directly virtually all the provisions of the original EU Constitution. As a result, the French and Dutch votes were ignored, and five governments have cancelled a promised referendum (Czech Republic, Denmark, Poland, Portugal and the UK). Only Ireland will have a referendum. The other 26 Member States will ratify the Lisbon Treaty in their parliaments without asking its people. Virtually every European Government has admitted that the Lisbon Treaty retained all of the important features of the EU Constitution.