A thermoplastic polymer composition that employs a flame retardant formed from a phosphinic compound and organometallic phosphoric compound is provided. The present inventor has discovered that the organometallic phosphoric compound can counteract the tendency of the phosphinic compound to degrade the mechanical properties of the composition when used at certain concentrations. Furthermore, the present inventor has also surprisingly discovered that the organometallic phosphoric compound may itself act as a flame retardant and thus contribute to the overall flammability performance of the composition. Among other things, this allows compositions to be formed with a lower phosphinic content with the same flammability performance.