Halogen-containing phosphoric acid polyesters of the general formula (I) ##STR1## IN WHICH R stands for an alkylene radical or a halogen-substituted alkylene radical having from 2 to 6 carbon atoms, a --CH.sub.2 CH.sub.2 --O--CH.sub.2 CH.sub.2 -- radical, a phenylene or an alkyl or halogenoalkyl-substituted diphenylenemethane radical, and R.sub.1 stands for a branched or unbranched alkyl radical having from 6 to 18 carbon atoms.