With reach of the mobile phone in the developing world unsurpassed by any other form of information communication technology, and its potential as a means to support learning widely recognised and the subject of a range of exploratory interventions, researchers, policy makers and practitioners have turned to the challenges of making mobile learning initiatives more scalable, more sustainable and more sensitive to the needs and circumstances of learners. At the same time, there is a call for a critical approach to the use of technology that serves to expose immanent knowledge and to challenge unequal power relations within educational settings, in order to identify ways in which educational technologies can be used in fairer and more equitable ways. This study employs action research, a methodological approach that I argue is appropriate for to address such an agenda. This thesis sets out the study of collaborative attempts to design and implement a mobile English language learning resource in partnership with a Non- Governmental Organisation (NGO) in Dharavi, Mumbai. Through three iterative action research cycles, conducted in a participatory manner with NGO leaders, teachers and students, this study investigates how the use of a mobile learning resource can provide a sustainable means of enhancing the learning of disadvantaged young adult participants enrolled on the NGO's Youth Empowerment Program. The design and use of a mobile learning resource is framed against a complex picture of young people's access, ownership and engagement with mobile technology, closely linked to gender, life stage and economic circumstance; as well as the NGO's shifting English language curriculum priorities and strategic change. The study reflects upon the nature of student learning experiences, through the use of the activities within the mobile learning resource itself, through broader strategies of digital engagement and through the participatory research process. Finally, the study identifies issues that constrain the sustained use of the mobile learning resource, including lack of flexibility and control over pedagogical content and the absence of continuing technical support.