In this paper we suggest a hybrid threshold approach for text-independent speaker verification. A maximum distortion (or minimum likelihood) threshold is set for the claimed speaker to perform pre-filtering of the highly dissimilar impostors. Cohort normalisation then is applied to further separate those impostors who are acoustically similar to the claimed speaker. A VQ-distortion based text-independent speaker verification system using this approach achieves better results than the conventional absolute threshold or cohort normalisation methods.