The Socialist group in the European Parliament has formed an alliance with the Italian Democratic Party (DP), a move that increases the grouping's MEPs by 21, to 182.
The decision was announced by Poul Nyrup Rasmussen, president of the Party of European Socialists (PES) on Friday.
The grouping will known as the Alliance of Socialists and Democrats for Europe (ASDE).
The Democratic Party was formed in October 2007 by merging the Democrats of the Left (DS) and the Margherita coalition of centre-left and liberal parties.
ASDE will have 182 MEPs, 82 fewer than the largest group, the European People's Party, which will have 264 members.
