A method for making a composite polyamide membrane comprising the steps of applying a polyfunctional amine monomer and polyfunctional acyl halide monomer to a surface of the porous support and interfacially polymerizing the monomers to form a thin film polyamide layer, wherein the method is includes at least one of the following steps: i) conducting the interfacial polymerization in the presence of a monomer comprising at least one phosphorous-containing functional group or salt thereof and an at least one amine-reactive functional group; and/or ii) applying such a monomer to the thin film polyamide layer.