The chief executive of Chicago Mercantile Exchange described the Intercontinental Exchange's rival bid for the Chicago Board of Trade as a "minnow swallowing a whale" and said ICE's offer was based on "false assumptions, dreams and exaggerated synergies".

ICE, the Atlanta-based electronic energy market, last week tabled a $9.9bn (€7.4bn) bid for CBOT, more than $1bn higher that the CME's agreed offer.