An electric power cable and a process for the production of the cable including a metal conductor and an electric insulation system surrounding the conductor coaxially and radially outwards of the conductor having improved electric properties. The insulation system includes an inner semi-conducting layer surrounded radially outwards by an insulation layer and wherein the insulation layer is surrounded radially outwards by an outer semi-conducting layer. The electric power cable further includes an inner water blocking material arranged in the conductor and/or to surround the conductor radially outwards and an outer water blocking material arranged radially outwards from the insulation system. An inner barrier layer is arranged as a diffusion hindering layer between the inner water blocking material and the insulation system and an outer barrier layer is arranged as a diffusion hindering layer between the insulation system and the outer water blocking material.