Mentioned in Fairbairn's endopsychic structural theory
This was originally described as internal saboteur in Fairbairn's 1944 paper, Endopsychic structure considered in terms of object-relationships. In 1954's Observations on the nature of hysterical states it was renamed antilibidinal ego.
Roughly overlaps with aspects of Freud's superego.
Fairbairn views superego (and its guilt) as a higher level overlay on top of the antilibidinal structure.