Answer ... Collective action is regulated by the Civil Procedure Act (OG SFRJ 4/77, 36/77, 6/80, 36/80, 43/82, 69/82, 58/84, 74/87, 57/89, 20/90, 27/90, 35/91, and OG 53/91, 91/92, 58/93, 112/99, 88/01, 117/03, 88/05, 02/07, 84/08, 96/08, 123/08, 57/11, 148/11, 25/13, 89/14, 70/19, 80/22).
Associations, bodies, institutions and other organisations established in accordance with the law which, within their registered or regulated activities, deal with the protection of collective interests and rights of citizens established by law can – if such authorisation is explicitly recognised and under conditions prescribed by that law – file a lawsuit for the protection of collective interests and rights against a natural or legal person that, by performing a specific activity or in general through its work or conduct (including omissions), severely infringes or threatens such collective interests and rights.
However, Croatian competition law has no special provisions for collective action. Hence, at the moment, it does not seem possible to bring a collective action for breach of competition law.