  Formation of transitory domain walls is quite generic in theories with
spontaneous breaking of discrete symmetries. Since these walls are in conflict
with cosmology, there has to be some mechanism which makes them disappear. We
study one such mechanism by incorporating Planck scale suppressed operators
within the framework of Left-Right Symmetric Models (LRSM) where Left-Right
parity (D parity) is spontaneously broken. We find that this mechanism can not
make the walls disappear in minimal versions of LRSM. We propose two viable
extensions of this model and show that Planck scale suppressed operators can
give rise to successful disappearance of domain walls provided the scale of
parity breaking obeys certain limits. We also constrain the scale of parity
breaking by demanding successful gauge coupling unification and make a
comparison of the unification and cosmology bounds.
