There is provided an imaging element having a flexible support and comprising on said support a photosensitive layer comprising a silver halide emulsion and an image-receiving layer comprising physical development nuclei, said layers being in water permeable contact with each other, characterized in that said flexible support is a polyester film having a thickness between 0.15 and 0.35 mm and consisting of polyethylene 2,6-naphthalenedicarboxylate. There is also provided a method for making a lithographic printing plate comprising the steps of image-wise exposing an imaging element as defined above and subsequently developing a thus obtained imaging element by an alkaline processing liquid in the presence of developing agent(s) and silver halide solvent(s).