  R parity violating trilinear couplings $\lambda'_{1jk}$ of the minimal
supersymmetric standard model (MSSM) are constrained from the limit on the
electron neutrino mass. Strong limits on these couplings follow from the
earlier neglected contribution due to sneutrino vacuum expectation values. The
limits on most of the $\lambda'_{1jk}$ couplings derived here are stronger than
the existing ones for a wide range in parameters of MSSM. These limits strongly
constrain the interpretation of recent HERA results in $e^+ p$ scattering in
terms of production of squarks through $R$ violating couplings. In particular,
the interpretation in terms of $\tilde{t}_L$ production off strange quark as
suggested recently is not viable for wide ranges in MSSM parameters.
