The disclosure relates to a method of manufacturing an implantable defibrillation coil for a lead of an active implantable medical device, the defibrillating coil includes at least one elongate conductive coil which includes a plurality of non-contiguous turns. The method includes inserting a tube of polymeric material within the elongated conductive coil, supplying thermal energy to soften the tube, applying pressure on the assembly formed by the elongate conductive coil and causing the tube to deform the tube wall by insertion of the tube wall between the turns of the elongate conductive coil.