A flame retardant composition comprising A. a thermoplastic vulcanizate composition comprising: 1. from 15 to 75 weight percent of a continuous phase comprising at least one thermoplastic polyester and 2. from 25 to 85 weight percent of a dispersed phase comprising at least one peroxide-cured elastomer selected from the group consisting of polyacrylate rubbers, polymethacrylate rubbers, polyethylene/polyacrylate rubbers, and polyethylene/polymethacrylate rubbers; wherein said rubber is dynamically crosslinked with at least one peroxide free radical initiator and at least one organic multiolefinic co-agent; the weight percentages of the continuous phase and the dispersed phase being based on the total combined weight of the continuous and dispersed phases, B. from 1 to 30 weight percent, based on the total weight of the flame retardant composition, of at least one flame retardant selected from the group consisting of phosphinates of formula I, diphosphinates of formula II, polymers thereof and combinations of two or more thereof wherein R 1 and R 2 are independently selected from hydrogen, linear or branched C 1 -C 6 alkyl groups, and aryl groups; R 3 is a linear or branched C 1 -C 10 -alkylene group, a C 6 -C 10 -arylene group, a C 6 -C 10 -alkylarylene a C 6 -C 10 -arylalkylene group; M is a metal ion selected from the group of calcium ions, magnesium ions, aluminum ions, zinc ions, and mixtures thereof, m is 2 to 3; n is 1 or 3; and x is 1 or 2; with the proviso that when m is 2, then x and n are each 1, and when m is 3, x is 2 and n is 3; and C. from 0.05 to 1.75 weight percent, based on the total weight of the flame retardant composition, of an ultra-high molecular weight polysiloxane which is a polysiloxane having a weight average molecular weight (Mw) of at least 100,000, the weight average molecular weight (Mw) being determined by gel permeation chromatography. A. a thermoplastic vulcanizate composition comprising: 1. from 15 to 75 weight percent of a continuous phase comprising at least one thermoplastic polyester and 2. from 25 to 85 weight percent of a dispersed phase comprising at least one peroxide-cured elastomer selected from the group consisting of polyacrylate rubbers, polymethacrylate rubbers, polyethylene/polyacrylate rubbers, and polyethylene/polymethacrylate rubbers; wherein said rubber is dynamically crosslinked with at least one peroxide free radical initiator and at least one organic multiolefinic co-agent; the weight percentages of the continuous phase and the dispersed phase being based on the total combined weight of the continuous and dispersed phases, 1. from 15 to 75 weight percent of a continuous phase comprising at least one thermoplastic polyester and 2. from 25 to 85 weight percent of a dispersed phase comprising at least one peroxide-cured elastomer selected from the group consisting of polyacrylate rubbers, polymethacrylate rubbers, polyethylene/polyacrylate rubbers, and polyethylene/polymethacrylate rubbers; wherein said rubber is dynamically crosslinked with at least one peroxide free radical initiator and at least one organic multiolefinic co-agent; B. from 1 to 30 weight percent, based on the total weight of the flame retardant composition, of at least one flame retardant selected from the group consisting of phosphinates of formula I, diphosphinates of formula II, polymers thereof and combinations of two or more thereof wherein R 1 and R 2 are independently selected from hydrogen, linear or branched C 1 -C 6 alkyl groups, and aryl groups; R 3 is a linear or branched C 1 -C 10 -alkylene group, a C 6 -C 10 -arylene group, a C 6 -C 10 -alkylarylene a C 6 -C 10 -arylalkylene group; M is a metal ion selected from the group of calcium ions, magnesium ions, aluminum ions, zinc ions, and mixtures thereof, m is 2 to 3; n is 1 or 3; and x is 1 or 2; with the proviso that when m is 2, then x and n are each 1, and when m is 3, x is 2 and n is 3; and C. from 0.05 to 1.75 weight percent, based on the total weight of the flame retardant composition, of an ultra-high molecular weight polysiloxane which is a polysiloxane having a weight average molecular weight (Mw) of at least 100,000, the weight average molecular weight (Mw) being determined by gel permeation chromatography.