The invention relates to a worktable clamping apparatus for releasably clamping a workpiece (W) between a pair of convergeable clamping edges of clamping jaws (1, 2) mounted on a supporting substructure. The apparatus is provided with an auxiliary support member (11, 11') connected thereto at a position (12a) at or above the upper frame (3) of the substructure. In use, the auxiliary support member(11, 11') presents an upper supporting surface between the respective clamping jaws (1, 2) but below the level of their clamping edges for supporting a workpiece (W) and/or a work-tool. The auxiliarysupport member (11, 11') may be in the form of a compartmentalised tray for storing tools or other auxiliary items. The auxiliary support member (11, 11') is displaceable relative to the respective clamping jaws (1, 2) between a first position in which it is retracted beyond a clamping edge of a clamping jaw (1) such that the surface area of its upper supporting surface is concealed beneath the clamping jaw (1), and a second position in which the surface area of its upper supporting surface at least partially protrudes beyond the clamping edge of the clamping jaw (1).