The Commission is one of the EU's key institutions. Until 1 May 2004 it had 20 members (two each from France, Germany, Italy, Spain and the United Kingdom, one from each of the other countries), appointed for a five year period by agreement between the Member States, subject to approval by Parliament.
On 1 May 2004, when 10 new member states joined the EU, the number of Commissioners also increased by 10. From 1 November 2004, the new Commission has only 27 members - one per country
The Commission acts with complete political independence. Its job is to uphold the interest of the EU as a whole, so it must not take instructions from any member state government. As "Guardian of the Treaties", it has to ensure that the regulations and directives adopted by the Council and Parliament are being put into effect. If they are not, the Commission can take the offending party to the Court of Justice to oblige it to comply with EU law.
The Commission is also the only institution that has the right to propose new EU legislation, and it can take action at any stage to help bring about agreement both within the Council and between the Council and Parliament.
As the EU's executive arm, the Commission carries out the decisions taken by the Council - in relation to the Common Agricultural Policy, for example. The Commission is largely responsible for managing the EU's common policies, such as research, development aid, regional policy etc. It also manages the budget for these policies.
The Commission is answerable to Parliament, and the entire Commission has to resign if Parliament passes a motion of censure against it. It was when faced with just such a motion of censure that President Jacques Santer tendered the collective resignation of his Commission on 16 March 1999. Romano Prodi became President of the Commission for the period 1999-2004 and since 2004 the president of the European Commissions is José Barroso.
The Commission is assisted by a civil service made up of 36 "Directorates-General" (DGs) and services, based mainly in Brussels and Luxembourg. Unlike the secretariats of traditional international organisations, the Commission has its own financial resources and can thus act quite independently.