  It is shown that the Bragg glass phase can become unstable with respect to
planar defects. A single defect plane that is oriented parallel to the magnetic
field as well as to one of the main axis of the Abrikosov flux line lattice is
always relevant, whereas we argue that a plane with higher Miller index is
irrelevant, even at large defect potentials. A finite density of parallel
defects with random separations can be relevant even for larger Miller indices.
Defects that are aligned with the applied field restore locally the flux
density oscillations which decay algebraically with distance from the defect.
The current voltage relation is changed to ln V(J) -J^{-1}. The theory exhibits
some similarities to the physics of Luttinger liquids with impurities.
