A flame retardant epoxy resin composition containing not more than 10% by wgt. of halogen, comprising an epoxy resin, stated concentrations of phosphoric acid ester, nitrogen—containing cross-linking agent having an amine functionality of at least 2 and a catalyst capable of promoting the reaction of the phosphoric acid ester with the epoxy resin and promoting the curing of the epoxy resin with the cross-linker, and optionally a Lewis acid in a stated amount.