The effect of an internal electric field built up along the Poly(dA)-poly(dT) DNA molecule on the electron transport in the molecule has been studied. The electric field dependent electron hopping amplitude has been used in the tight-binding Hamiltonian model of a Poly(dA)-poly(dT) DNA molecule. Green's function technique is used in calculating electron transmission probability, which is then used for computing current as a function of voltage by employing the Landauer-Büttiker formalism. It is observed that the internal electric field can cause the current decreases with voltages. The current reaches its maximum at a lower voltage as the internal electric field increases. © Published under licence by IOP Publishing Ltd.