Party politics is largely irrelevant in the EU institutions. The exception is the European Parliament, where most MEPs sit in one of seven political groups. These groups are not organized by nationality, but rather by political beliefs. MEPs who do not belong to a political group are known as Non-Inscrits (NI).
No group has an overall majority in the European Parliament. This means that consensus among a number of political groups is needed in order that the decision-making process, e.g. making legislation, presenting written declarations, may progress. Since the Lisbon Treaty came into force in 2009, establishing consensus among a number of political groups has become particularly important. The reason is that the European Parliament is co-legislator with the Council of the European Union on approximately 80% of new EU legislation. As a result, if the political groups cannot work with each other, new EU legislation risks being significantly stalled.
At time of writing there are approximately 750 MEPs, about 30 of which are not attached to any political group. The others belong to one of the following groups:
The European People’s Party (EPP). This is the main centre-right group and comprises approximately 270 MEPs;
The Progressive Alliance of Socialists and Democrats (S&D). This is the main centre-left and socialist group and comprises approximately 190 MEPs;
The Alliance of Liberals and Democrats for Europe (ALDE). This is the centrist group and comprises approximately 85 MEPs;
Greens/European Free Alliance (Greens/EFA). This joint group is composed of various environmentalists, regionalists and nationalists and comprises approximately 60 MEPs;
European Conservatives and Reformists (ECR). Formed of those MEPs who opposed the pro-EU stance of the EPP. It numbers approximately 50 MEPs;
Confederal Group of the European United Left (GUE)/Nordic Green Left (NGL). This joint group is formed of far left and communist politicians and comprises approximately 35 MEPs; and
Europe of freedom and democracy Group (EFD). This is a group formed of hard line nationalists and Eurosceptics and numbers approximately 30 MEPs.