A deal combining Eon and Endesa is certain to face careful scrutiny by antitrust regulators, many of whom are deeply concerned about the state of competition in Europe’s energy markets.

Neelie Kroes, the European Union competition commissioner, warned only last week that she would keep a close watch on further consolidation in the electricity and gas sectors. She and her officials in Brussels believe that Europe’s energy markets already suffer from a high degree of market concentration that has stifled competition and frozen out potential new market entrants.