A cable connector clamp for an insulated electrical cable is preferably integrally moulded from a resilient plastic material. It has a cylindrical housing defining a passage for the cable, and a slot to permit its insertion into a knock out or opening of an enclosure wall. Within the housing, there is a clamping element extending across the passage and resiliently deflectable, to permit insertion of a cable. The clamping element includes a clamping lip that is resiliently pressed against the cable to prevent its withdrawal from the connective clamp. To assist in clamping the cable, one or both of a clamping lip of reduced thickness at the free end of the clamping element, and additional projections on the inner wall of the housing are provided. The additional projections have abutment faces, perpendicular to the axis of the housing and facing the second end of it.