Translate the following English sentence to French:
"I believe that these practices, as well as the possible substitution of the well-known national monopolies by a European oligopoly, should be combated relentlessly by the services which come under the responsibility of the Commission."
Je pense que ces pratiques et l'éventuel remplacement des monopoles nationaux connus par un oligopole européen doivent être implacablement poursuivis par les services de la concurrence de la Commission.