Introduction: The fight against labour exploitation has received increasing attention globally, and has largely focused on migrant workers or sectors where they are mostly employed. In the United Kingdom (UK), for instance, labour exploitation is covered by the Modern Slavery and Immigration Acts, thereby connecting exploitation and migration. In public health, the lack of a common understanding of what exactly constitutes labour exploitation for migrant workers has limited the study of its impacts on migrant workers' health, and hindered the generation of evidence to inform policies and provide appropriate healthcare to address exploited migrant workers’ needs. Aim: This thesis aims to clarify the concept of labour exploitation focusing on migrants working in manual low-skilled jobs, by providing a structured conceptual framework using professional experts’ and migrant workers’ voices. It builds on the growing conceptualisation of labour exploitation as a continuum “between decent work and forced labour” (1). Methods: The main method used was Concept Mapping (CM). It was undertaken with two groups: 1) multidisciplinary professional experts; and 2) Latin American migrant workers in London (LAWs). A critical analysis and synthesis compared and combined both groups’ perspectives. Interviews with LAWs and key informants working with them were also used to prepare for the CM with LAWs and explore the issue of migrant workers’ exploitation in the UK context. Key findings: The expert CM generated the main structured conceptual framework, which revealed four main dimensions of labour exploitation: ‘Shelter and personal security’, ‘Finance and migration’, ‘Health and safety’, and ‘Social and legal protection’. The CM with LAW displayed three main dimensions: ‘Poor employment conditions and lack of protection’, ‘Health and safety and psychosocial hazards’ and ‘Disposability and abuse of power’ (or ‘Dehumanisation’). The adaptation of the expert skeleton map using LAW’s voices integrated the new dimension of ‘Dehumanisation’ and structural forms of coercion. Furthermore, the analysis of the interviews led to identifying an ecosocial model of labour exploitation, revealing micro (e.g. workplace) and macro (e.g. national) levels of labour exploitation. Conclusion: This thesis posits labour exploitation as a social determinant of migrant workers’ health, and clarifies its content based on professional experts’ and migrant workers’ inputs. The conceptual framework offers an operational tool that could support the development of a common body of evidence about the impact of labour exploitation on migrant workers’ health.