Dielectric investigations of the photoinduced effects in the vicinity of the smectic A (Sm-A)–antiferroelectric smectic C (Sm-CA*) transition of a guest–host system consisting of photoactive azobenzene-based guest molecules and non-photoactive host molecules have been carried out. The frequency-dependent dielectric data is analysed in terms of a molecular mode and a high-frequency mode. We observe that the dielectric parameters associated with the two modes show primary as well as secondary photoferroelectric effects, in agreement with the effects observed in our previous study (Nair et al 2006 Phys. Rev. E 73 011712, referred to as [1] in the present article) for polarization and response time. Here the primary photoelectric effect is associated with changes in the polar ordering and/or transverse molecular dipole moment at a constant reduced temperature and the secondary effect is due to the radiation-induced reduction in the transition temperature. The temporal variation of the relaxation parameters shows that the photoinduced isothermal transition as well the thermal back relaxation occurs on fast timescales.