An anodized aluminum support for use in a lithographic printing plate comprises a bilayered anodic surface having a total average thickness of at least 0.10 micrometers consisting essentially of oxides and phosphates of aluminum present in a coverage of greater than 100 milligrams per square meter of support. The anodic surface comprises an upper stratum comprising pores having an average diameter of 1.0.times.10.sup.-8 -7.5.times.10.sup.-8 m and a lower stratum comprising pores having an average diameter substantially greater than the pores in the upper stratum. The support is prepared by a two-stage process of anodically oxidizing at least one surface of an aluminium plate in an aqueous electrolyte comprising phosphoric acid under conditions wherein the upper stratum is formed in the first stage and the lower stratum is formed in the second stage. A lithographic printing plate comprising a radiation-sensitive layer and the above-described support exhibits improved resistance to staining.