The European Commission has launched infringement procedure against Spain over its failure to comply with commission decisions on proposed acquisition in the energy sector, said the commission on Wednesday.

The commission has formally requested Spain to explain why it has not complied with the commission's decisions requiring the withdrawal of certain conditions concerning German energy giant E. ON's bid for Spain's Endesa imposed by the Spanish authorities in July 2006 and in November 2006.

The request takes the form of a complementary "letter of formal notice," the first stage of infringement proceedings.

If there is no satisfactory reply within 15 working days, the commission, the executive body of the European Union, may decide to issue a formal request in the form of a "reasoned opinion," the second stage of infringement proceedings.

The conditions imposed by the Spanish authorities were declared illegal by the commission in September 2006 and December 2006 respectively.