Even though an electric field E exerts a force qE on a charged particle yet the electric field of an EM wave does not contribute to the radiation pressure (but transfers energy). Explain.

The electric filed of the electromagnetic wave is oscillating in nature. This electric field applies electric force on the charged particle, the average electric force for integral cycle is zero as the direction changes for every half cycle. So, electric field does not cause the radiation pressure but it transfers energy. The action of the magnetic field of the electric current induced by the electric field of the same wave causes the radiation pressure.