As the political system of the European Union (EU) is characterised by pluralism, the study of interest representation in the EU has developed since the mid-1980s. While the study of EU lobbying has focused on lobbying aimed at the European Commission as the agenda-setter, lobbying aimed at the European Parliament (EP) has recently become an point of critical focus due to the growing role of the EP in EU policymaking. The role of political groups in lobbying aimed at the EP has made scholars inspired by lobbying studies which focus on the United States Congress. While some argue that interest groups mainly lobby political groups supporting their aims (friendly political groups), it has also been pointed out that groups lobby political groups that work against their aims (unfriendly political groups) as well. The latter argument emphasises the importance of these political groups’ size when lobbies choose to target unfriendly groups. However, an interest group’s incentive for lobbying would naturally be lowered if most members of a large unfriendly political group had different preferences than the interest group. In the reverse, the incentive would become higher if a large unfriendly political group was experiencing internal division and some members of the group shared similar preferences with those of the interest group.

With this point in mind, this article analyses lobbying aimed at political groups in the EP, focusing on how interest groups decide to target unfriendly political groups. When the European Commission’s preference regarding a certain policy issue is divergent from that of the EP, interest groups have more incentive to lobby the EP in order to change or maintain institutional balance among EU institutions. Therefore, to exemplify this situation, this article conducts a pilot case study about interest groups’ lobbying on Trade and Sustainable Development (TSD) clauses in free trade agreements (FTAs) of the EU.

It firstly concludes that, according to the author’s interviews of interest groups and political groups in 2018, business associations and NGOs had direct contacts with members not only of friendly political groups but also of unfriendly groups. Additionally, when these groups chose to target unfriendly political groups, they took into account the groups’ ‘cohesiveness’ as well as their size. However, since trade unions did not lobby unfriendly political groups, this hypothesis on the relationship between lobbying and political groups’ ‘cohesiveness’ could be dependent on the type of interest groups. Secondly, the analysis of the EP discussion in the 7th–8th EP clarifies the gap between political groups’ cohesion (coherence of preferences) and interest groups’ perception of their ‘cohesiveness’, specifically in terms of centre-left and centre-right political groups. Finally, this article’s analysis could be more relevant to the 9th EP, where political groups’ configurations have become more fragmented.