A light-sensitive lithographic printing plate element suitable for the formation of negative and positive images, simultaneously, comprising a hydrophilic support having, in succession, a light-sensitive composition layer and a transparent cover film in which images for printing are formed by imagewise exposing through the cover film and peeling apart to remove, together with the cover film, the areas having a stronger adhesion to the cover film in the light-sensitive composition layer by utilizing the difference in adhesion to the support and to the cover film between the exposed areas and the unexposed areas of the light-sensitive composition layer, whereby the areas of the light-sensitive composition layer having a stronger adhesion to the support remain on the support, wherein the surface of the support adjacent the light-sensitive composition layer is treated with an aqueous solution containing at least one water soluble oxygen acid or water soluble oxygen acid salt selected from the group consisting of boric acid, boric acid salts, molybdic acids, molybdic acids salts, phosphoric acids, phosphoric acid salts, vanadic acids, vanadic acid salts, tungstic acids, tungstic acid salts, chromic acid, chromic acid salts, silicic acids and silicic acid salts.