Eurex, the world's biggest derivatives exchange, is taking legal action against the Chicago Board of Trade and the Chicago Mercantile Exchange alleging they have illegally attempted to block its entry into the US market.

In an extraordinary new twist, the German to Swiss owned exchange claims that the CBOT and CME have violated the Sherman Act by offering financial inducements of at least $100m (€85.53m) to shareholders of The Clearing Corporation to vote against a proposed restructuring of the company.