The dielectric behaviour of an electroclinic ferroelectric liquid crystal has been investigated by dielectric relaxation method in the frequency range of 50Hz-10MHz in a thick (6.5μm) cell. The results have been reported in a planarly aligned sample, where the measuring electric field is perpendicular to the director and parallel to the smectic layer planes. It is observed that in the phase transition region from Sm C * -Sm A, the collective dielectric processes such as Goldstone and soft mode could not be separated. These two dielectric processes are reported and discussed as a function of temperature and bias voltages in Sm C * and Sm A phases and near the phase transition temperature.