There is provided herein a flame-retarded polyolefin composition comprising a thermoplastic polyolefin, an inorganic flame retardant filler and a metal phosphonate or metal phosphinate synergist of the general formula (A): where Me is a metal, R1 and R2 are the same or different linear or branched or cyclic alkyls having up to 6 carbon atoms, or benzyl, n is a metal valency and can be, 1, 2, 3 or 4, x is 1 for metal phosphonates and x is 0 for metal phosphinates. There is also provided a method for making a flame-retarded polyolefin composition comprising contacting at least one thermoplastic polyolefin polymer with at least one inorganic flame retardant filler and at least one metal phosphonate or metal phosphinate synergist and heating the mixture to above the melting temperature of the thermoplastic polyolefin.