Process for the posttreatment of an imaged lithographic printing plate comprising (a) providing a lithographic printing plate comprising image areas and non-image areas on a lithographic substrate; (b) bringing the lithographic printing plate of step (a) into contact with a solution comprising a hydrophilic polymer comprising structural units derived from the following compounds: (i) a compound comprising both polyalkylene oxide chains and at least one structural unit which is free-radical polymerizable, and (ii) a monomer capable of copolymerizing with the free-radical polymerizable structural unit of (i) and furthermore comprising at least one acidic functional group with pKs