  Unified models incorporating the right handed neutrino in a symmetric way
generically possess parity symmetry. If this is broken spontaneously it results
in the formation of domain walls in the early Universe, whose persistence is
unwanted. A generic mechanism for destabilisation of such walls is a small
pressure difference signalled by difference in the free energy across the
walls. It is interesting to explore the possibility of such effects in
conjunction with the effects that break supersymmetry in a phenomenologically
acceptable way. Realising this possibility in the context of several scenarios
of supersymmetry breaking results in an upper bound on the scale of spontaneous
parity breaking, often much lower than the GUT scale. In the left-right
symmetric models studied, the upper bound is no higher than $10^{11}$GeV but a
scale as low as $10^5$GeV is acceptable.
