The first paragraph of Article 197 of the Treaty establishing the European Community (TEC) as well as the future(?) Lisbon Treaty Article 14(4) of the Treaty on European Union (TEU) let the European Parliament decide freely on most of its internal organisation.
Rules of Procedure
The main text in this respect is the Rules of Procedure (16th edition, October 2008), available at:
Group and strength
The Rules of Procedure make it quite clear that the political groups run the show. After a recent amendment ─ Resolution P6_TA(2007)0499 ─ only one of the non-attached members (non-inscrits, NI) is allowed to attend the meetings of the Conference of Presidents, without a vote.
Among the political groups, the bottom line is that the larger ones decide. Even if each group is represented in the Conference of Presidents, the chairs of the political groups vote according to the parliamentary strength of their groups:
Rule 23 Composition of the Conference of Presidents
1. The Conference of Presidents shall consist of the President of Parliament and the chairs of the political groups. The chair of a political group may arrange to be represented by a member of that group.
2. The non-attached Members shall delegate one of their number to attend meetings of the Conference of Presidents, without having the right to vote.
3. The Conference of Presidents shall endeavour to reach a consensus on matters referred to it.
Where a consensus cannot be reached, the matter shall be put to a vote subject to a weighting based on the number of Members in each political group.
The requirements for a political group will be treated in a later post.