The European Union is preparing to clamp down on energy giants that control both the supply of energy and the infrastructure to deliver it, Neelie Kroes, the competition commissioner, said on Monday.

Splitting up integrated energy firms, such as RWE and Eon of Germany and the French group EdF, would be an “absolute priority” for her to stimulate cross-border competition and solve the insufficient level of unbundling in the sector, Ms Kroes told an energy conference in Lisbon.