  We revise a recently proposed mechanism for spontaneous CP breaking at finite
temperature in the Higgs sector of the Minimal Supersymmetric Standard Model,
based on the contribution of squarks, charginos and neutralinos to the one-loop
effective potential. We have included plasma effects for all bosons and added
the contribution of neutral scalar and charged Higgses. While the former have
little effect, the latter provides very strong extra constraints on the
parameter space and change drastically the previous results. We find that CP
can be spontaneously broken at the critical temperature of the electroweak
phase transition without any fine-tuning in the parameter space.
