The interaction between air quality and play space receives less focus in planning than it has in public health and environmental sciences research. In this paper, seven local planning authorities of inner London (UK) were sampled from the 10 boroughs with the worst air quality in parks. Greenwich, with significantly better air quality, was included for comparison. The selected authorities were validated against deprivation data, ensuring variance in socio-economic terms. Across this sample, 21 major residential planning applications were assessed, alongside a document analysis of planning policy documents for each authority. Lastly, five semi-structured interviews with different practitioners collectively provided multi-disciplinary perspectives on the planning processes across the sample. Despite the national government having conferred children a right to leisure space and a healthy environment via international conventions, the English planning system, as an institutional rights framework, is not consistently prioritising the delivery of children’s play space nor delivering play space where the air quality has been robustly assessed. In other words, such rights have been subjugated to other priorities in limited urban space in London. Therefore, a discretionary planning system does not preclude individual human rights from becoming disadvantaged under democratically controlled decision-making processes.