  In this paper we will study the spontaneous breakdown of the Lorentz symmetry
by ghost condensation in perturbative quantum gravity. Our analysis will be
done in the Curci-Ferrari gauge. We will also analyse modification of the BRST
and the anti-BRST transformations by the formation of this ghost condensate. It
will be shown that even though the modified BRST and the modified anti-BRST
transformations are not nilpotent, their nilpotency is restored on-shell.
