The Landau-de Gennes model of the boundary layer phase transition in nematic liquid crystals is extended to include electric field effects. Calculations are performed in the case of a semi-infinite nematic sample bounded by a solid wall. The phase diagrams presented show that the prewetting transition can be induced by the electric field. The transition moves to higher temperature with increasing field and disappears above the prewetting critical point. A system exhibiting partial wetting should transit to complete wetting under a high enough electric field. These predictions are confirmed within the actual experimental limits.