Niobium based glasses of composition Na2NbMP3O12 (where M = Cd, Zn, Pb and Cu) have been synthesized by melt quenching method and characterized by XRD, FTIR and DSC. The ac conductivity measurements have been carried out over wide range of frequencies at different temperatures on these glassy systems. Ac conductivity data are analyzed using conductivity and electric modulus formalisms. The bulk dc conductivity obtained from complex impedance plots follow the Arrhenius behavior and its activation energy matches well with the activation energy obtained from electric modulus formalism. The ac conductivity plot exhibits universal power law features and the temperature dependence of dc and ac conductivity is discussed. The scaling behavior of the ac conductivity and electric modulus spectra with respect to temperature are discussed and reported for these glassy systems. (c) 2009 Elsevier B.V. All rights reserved.