The present invention relates to an oxidizing composition for treatment of keratin fibers comprising a combination of; (a) at least one anionic associative copolymer, (b) at least one anionic non associative copolymer; (c) at least one peroxide agent; (d) at least one persulfate agent; (e) at least on alkalizing agent; and (f) a carrier medium suitable for hair treatment. The oxidizing composition described is suitable for composition used in conventional hair treatments such as dyeing, bleaching, and permanent waving or relaxing/straightening of the keratinous fibers, particularly human hair, requiring an oxidizing composition.