We study supersymmetric models without R parity and with universal soft supersymmetry breaking terms. We show that as a result of the renormalization group flow of the parameters, a misalignment between the directions in field space of the down-type Higgs vacuum expectation value $v_d$ and of the $��$ term is always generated. This misalignment induces a mixing between the neutrinos and the neutralinos, resulting in one massive neutrino. By means of a simple approximate analytical expression, we study the dependence on the different parameters that contribute to the misalignment and to $m_��$. In large part of the parameter space this effect dominates over the standard one-loop contributions to $m_��$; we estimate 1 MeV $\lsim m_��\lsim 1 GeV$. Laboratory, cosmological and astrophysical constraints imply $m_��\lsim 100 eV$. To be phenomenologically viable, these models must be supplemented with some additional mechanism to ensure approximate alignment and to suppress $m_��$.

21 pages, LaTex. Few points clarified, results unchanged. Final version to appear on Physical Review D