In investigating recent changes to the automotive industry production process, such as modularisation, our work emphasises the process of fragmentation of production as a configuring element of inter-firm power relationships, and as an explanatory element in working conditions. From a theoretical framework focused on power relations, we analyse by way of a selected case study how the capabilities of companies and their network positions, together with the agency of labour, shape the power relations that influence the evolution of working conditions. The study does indeed find relevant changes to inter-firm relationships, for example, within networks of assemblers and suppliers, but without a consequent re-balancing of power. This finding serves to explain differences in the evolution of working conditions between distinct companies, these conditions being fully functional to a strategy for profitability and thus difficult to reverse. JEL Codes: J31, L14, L62