In this paper a Gaussian mixture model (GMM) classifier, called GMM identifier, is proposed as an efficient post-processing method to enhance the performance of a CMM-based speaker verification system; such as Gaussian mixture model universal background model (GMM-UBM) and structural Gaussian mixture models with structural background model (SGMM-SBM) speaker verification schemes. The proposed classifier shows good performance while its computational load is almost negligible compared to the main GMM system. Experimental results show the superior performance of this post-processing method in comparison with a neural-network post-processor for such applications.