A two‐ and one‐half‐dimensional electromagnetic particle code (PS2M) [H. Abe and S. Nakajima, J. Phys. Soc. Jpn.53, xxx (1987)] is used to study how an electric field applied parallel to the magnetic field affects the radio frequency stabilization of flute modes in a tandem mirror plasma. The parallel electric fieldE∥perturbs the electron velocityv∥parallel to the magnetic field and also induces a perpendicular magnetic field perturbationB⊥. The unstable growth of the flute mode in the absence of such a radio frequency electric field is first studied as a basis for comparison. The ponderomotive force originating from the time‐averaged product ⟨v∥B⊥⟩ is then shown to stabilize the flute modes. The stabilizing wave power threshold, the frequency dependency, and the dependence on ∇‖E∥‖ all agree with the theoretical predictions.