The European Commission said Wednesday it had "no alternative" but to veto a transatlantic tie-up of the Frankfurt and New York stock exchanges, a decision slammed in Germany as a "dark day" for Europe.

The European Union's senior competition regulator Joaquin Almunia confirmed in Brussels the long-anticipated decision to block the planned merger on the grounds the combined company would con-trol90 percent ofakey sector.

The trade in certain derivatives products on such exchanges and whose values are dependent on underlying European economic fundamentals, Almunia said, would become skewed because the joint company would dominate the global market there. "We could only have allowed a merger if the parties had offered sufficient remedies," Almunia said in reference to conditions involving disposals by both set down by the Commission last year for the EU to give its green light.

"Unfortunately they only offered remedies limited in their scope,"hesaid.

As a result, "in the end, we had no alternative other than to prohibit the merger."