Maastricht Treaty

Jacques Delors said "oui" but not everyone agreed

Maastricht is perhaps the best known and most controversial of the European treaties.

It became renowned not only for the long and fractious negotiations and baffling terminology involved in drafting it, but also for the difficulties many member states had in ratifying it.

Maastricht is officially known as the Treaty of the European Union and with it the EU came into existence for the first time.

By adding two new areas - justice and home affairs and a common foreign and security policy - to the existing European Community, the so-called three pillars of the Union were established.

The people of the 12 member states were also given European citizenship.

They now have the right to move and live in any EU state and may vote in European and local elections in any country.

Maastricht was also the blueprint for what was to be Europe's biggest project for the next decade - economic and monetary union.

It defined the three stages of EMU which eventually led to the single currency, and set out the convergence criteria or economic tests that member states have to pass.

The treaty also introduced integration in employment and social issues - at least for some members.

The UK negotiated an opt-out of the so-called social chapter - a part of the treaty which was eventually adopted as a protocol and which covered issues such as workers' pay and health and safety.

Although, after a change of government, the UK did finally sign up to the social chapter, another aspect of Maastricht - subsidiarity - has remained a bugbear for Europe.

Subsidiarity is the principle whereby the Union does not take action (except in the areas which fall within its exclusive competence) unless it is more effective than action taken at national, regional or local level.

The treaty explicitly recognised the principle of subsidiarity for the first time, but while some have interpreted this as prioritising the rights of national and local governments, others see it as giving more power to the EU.

But even once all this had been thrashed out at the summit in 1991, the treaty had a tough time coming into force.

It was first rejected by a Danish referendum, and then after some alterations scraped through.

France also gave Maastricht a less than enthusiastic response - its referendum approved the treaty by a tiny margin.

In Germany it was sent to the constitutional court, which in the end voted for it. In the UK, it squeezed through parliament under unprecedented pressure. It finally came into force in November 1993.