In this article we explore the emergence of a cluster of social movement organisations that have critically taken issue with nanotechnology in Germany, the UK and internationally. By applying concepts borrowed from Social Movement Research we demonstrate that this cluster is a ‘spin-off’ from the preceding movement against agrofood biotechnology, however, never succeeds in mobilizing a comparable ‘antinanotechnology movement’. We argue that the turn toward participatory and deliberative practices that is characteristic of nanotechnology policy and, to a major extent, is (...) based on the perceived threat of a ‘public backlash’ against nanotechnology, while being of little political impact, reinforces the activity of these critical organisations through the provision of political opportunities. We further argue that the stagnation of these organisations can be explained by low policy impact and low public responsiveness respectively and conclude that their trajectories hinge to a major extent on policy impact and the responsiveness of the mass-public. We end by making a concluding remark about the limits to the project of democratizing social contention through public engagement. (shrink)