The groups of experts of the European Commission have been, until recently, among the least visible actors of the government of Europe. Unlike the working groups of the Council (gathering representatives of the Member States and intergovernmental negotiations), or 'comitology committees' (consisting of officials from Member States assisting the Commission in its executive functions), these groups are solely accountable to the Community administration (de Maillard, Robert, 2008). Focused on preparatory and exploratory work, and composed of external actors with various statuses, these groups have a strictly consultative role. However, they are active in a crucial, yet weakly publicised phase of the European decision-making process: the preliminary stages of problem definition. Numbering approximately eight hundred in number, expert groups have rarely attracted the attention of the media, apart from a few notable exceptions, such as that for instance of the 'Sapir group' (Peuziat, 2005). Nonetheless, in the Spring of 2009, they found their way into the media spotlight during highly publicised and heated exchanges between certain interest groups and the Community administration. The NGO Corporate UE Observatory, which has become visible over the past ten years through its crusades denouncing the power of business lobbies in the European political system, published a report on March 25 2008 suggestively entitled 'Culture of secrecy and companies' dominationa study of the composition and of the transparency of the Expert Groups in the European Commission' (Alter EU/CEO, 2008) 1. Published by the ALTER EU network (Alliance for Lobbying Transparency and Ethics Regulation), the document analysed the composition of some forty expert groups. It simultaneously denounced the opaque operation of these authorities and the massive presence of representatives of industry, which was seen to produce both discreetly and efficiently a strong pro-industry bias in the European decision-making processes. If this controversy took place in series of public actions raising issues relative to transparency and the problematic relationships between the Commission and interest groups, it also echoed repeated complaints 1 Expert groups has become one of the main focuses of the criticisms of Alter EU questioning the 'fair balance' of interests'. They published several reports: 'A captive Commission : the role of the financial industry in