The influence of the polymer network density formed in short pitch ferroelectric liquid crystal on the electroclinic effect has been analyzed. The polymer network is formed from a photo-reactive achiral monomer in a thin planar S(c)* cell. Using an electro-optic response technique, the electric field dependance of the induced tilt angle and the polarization near to the S(A)-S(c)* transition has been measured for different polymer concentrations. The results show that at phase transition temperature the electroclinic effect and the electroclinic susceptibility are largely controlled by the polymer network. These results are discussed and applied to a simple phenomenological model developed in [20]. This model confirms our observations for all of the polymer concentration studied. The average distance between two fibers and the interaction energy between the liquid crystal molecules and the polymer network are estimated. Good correlation is found between the experimental results and the proposed model.