Deutsche Börse is to sue the European Commission over its decision to block a proposed $9 billion merger with Nyse Euronext.
Anti-trust officials at the Commission vetoed the proposed tie-up last month over fears that the deal would stifle competition in the derivatives markets.
European Commission antitrust chief Joaquin Almunia had demanded that Deutsche Börse and Nyse sell either the Eurex derivatives arm or Liffe if they wanted the deal to go ahead, a course of action which neither exchange was prepared to countenance.
Deutsche Börse, which had spent €80 million in project expenses during 2011 to bring about the planned merger, described the decision as a "black day" for Europe and for its future competitiveness on global financial markets.
The German exchange operator says it will take its case to the general court in Luxembourg. Nyse - which estimated its costs at $85 million - has yet to decide whether to join the action, which is likely to take over a year to grind through the courts.