A vehicle seat backrest suitable for allowing the attachment of a child seat, the backrest comprising a rigid structure and an anchoring system comprising an anchor rod to permit to a coupling member belonging to the child seat to be anchored on the anchor rod via the rear face of the rigid structure. The anchoring system comprises a rigid plate comprising retainer suitable for retaining the anchor rod by abutment contact when the coupling member of the child seat exerts forces on the said anchor rod.