We show that the universal α-attractor models of inflation can be realized by including an auxiliary vector field for the Starobinsky model. If the same procedure is applied to general modified f(R) theories, we obtain the Brans-Dicke theory with a scalar potential. We also place observational constraints on inflationary models based on auxiliary vector modified f(R) theories from the latest Planck measurements of the Cosmic Microwave Background (CMB) anisotropies in both temperature and polarization.