A new technique for the measurement of the surface profile of optical surfaces of long radius of curvature is presented. A phase shifting lateral shearing interferometer is used. Laterally sheared wavefronts are generated due to Fresnel reflections of the test wavefront at oblique incidence from the (plane parallel and separated) inner surfaces of a pair of glass wedge plates. A pair of matched wedge plates, which together form a parallel plate, whose thickness can be varied by translating one of the wedges, is used to introduce phase shifts between the laterally sheared components. Surface slopes and profile are determined by applying phase shifting interferometry. An optical setup for measurement of surface profile of beam line mirrors of synchrotron radiation sources is proposed.