The effect of thermal plasma on the whistler wave propagation in the presence of an electric field parallel to the geomagnetic field lines has been investigated. The dispersion equation accounting for the effect of the parallel electric field in thermal plasma including the resonant particles has been derived. Analysis of the dispersion equation shows that the real part of k is slightly affected by the electric field and the whistler wave suffers damping or growth with varying whistler wave frequencies. It is found that a state of marginal stability is reached at a critical wave frequency counterbalancing the thermal damping by the electric field instability.