An insert for embedment in a concrete component during casting, having a tubular cavity for receiving a threaded anchorage member, the tubular cavity having an opening arranged to face outward of the concrete component when cast for insertion of the threaded anchorage member, wherein the insert is externally tapered such that, when the insert is embedded in the concrete component and the anchorage member is threadedly engaged within the tubular cavity, axial loading applied to the anchorage member in a sense to withdraw the anchorage member from the insert causes reactional force from the surrounding concrete to be applied to the insert in a direction radially inwardly of the insert, and wherein the insert is formed of deformable plastic material such that said reactional force in turn causes the insert to exert force radially inwardly upon the anchorage member.