The present invention relates to a surfactant composition for use in glyphosate-containing herbicide formulations, comprising from 5 to 50% by weight of one or more amphoteric surfactants, diluted in solvents derived from the process of synthesis thereof, wherein the surfactants have general formula (I) €ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒ€ƒR 1 -(XR 2 ) m -N + (R 3 )(R 4 )-CH 2 -CH(R 5 )-COO - €ƒ€ƒ€ƒ€ƒ€ƒ(I) wherein R 1 is hydrogen or C 1-18 hydrocarbyl; each X is independently an ether, thioether, sulfoxide, ester, thioester or amide bond; each R 2 is independently a C 3-6 chain; m is a number from 0 to 8 such that the number of carbon atoms in R 1 - (XR 2 ) m is from 8 to 24; R 3 and R 4 are independently hydrogen or C 1-4 chains; R 5 is hydrogen or methyl. The surfactant composition is used to increase the agronomic efficacy of herbicide formulations containing a high concentration of glyphosate salts. The present invention further describes herbicide formulations comprising such surfactant composition as well as the use thereof.