Through our parent-practitioner-community (PPC) partnership, consisting of parents with children involved with social work, infant mental health practitioners, researchers, and community stakeholders, we have coproduced Infant Parent Support teams (IPS), in Glasgow and London. IPS are mental health teams offering high quality therapeutic interventions to struggling families. IPS teams aim to reduce the risk of child maltreatment (CM) and improve parent and child mental health. In this study, we propose to further develop the place-based features of IPS teams and test the clinical and cost-effectiveness of IPS in a definitive randomised controlled trial (RCT). Place-based inequalities in health begin early in childhood: young children experiencing poverty and/or racism are more likely to develop health problems earlier in the lifespan than their peers. Children in the most deprived 10% of small UK neighbourhoods are over 10 times more likely to be in care or on protection plans than children in the least deprived 10%. Social determinants of health and child welfare are "systemic, population-based, cyclical and intergenerational" resulting in certain geographical areas being plagued by overlapping physical and mental health problems and addictions. Infants and preschool children rely on parents and practitioners access services - a process vulnerable to structural inequalities. Our novel aim is to redress this. Our coproduction has led to enhancements of IPS, including neurodevelopmental awareness, poverty awareness, and the employment of parents as practitioners and managers in IPS, and we have mapped the local contexts in which the IPS teams are embedded. We are currently conducting a feasibility randomised controlled trial (f-RCT) investigating how best to involve the families who can benefit most from IPS. In this new study, consisting of four work packages (WPs), we aim to reduce place-based inequalities through: WP1, co-creating a new theory of change for IPS that takes the local context in which IPS teams are embedded into account; WP2, implementing findings from our f-RCT and WP1 to make IPS teams fully place-based, i.e., further embedding IPS teams within their local communities and enhancing each local community's ability to make best use of IPS; WP3 (contiguous with WPs 1, 2 and 4), conducting a definitive RCT to examine the clinical and cost-effectiveness of IPS in reducing the risk of child maltreatment and improving mental health; and WP4, conducting a realist process evaluation examining what works best, for whom and in what context. RCT outcomes will also include measures of community connectedness and IPS costs, consequences and cost-effectiveness. At two adaptation points during the RCT, all four WPs will work with an expert scientific advisory group and the PPC-partnership to examine whether we are reaching our desired target population (including marginalised families) and, if not, to enhance our recruitment strategy to achieve equality of access to the study by employing recruiters who come from or have links with under-served populations, and/or targeting specific geographical areas through our extensive networks across Greater Glasgow and in ten diverse London Boroughs. Our success in reducing place-based inequalities will be measured by whether our RCT has recruited a trial population that demographically mirrors our target population. The techniques most successful in achieving this will inform recommendations for post-trial implementation of IPS to ensure that future IPS teams can reduce place-based inequalities by embedding optimally within their local community/service context, and targeting the families likely to most benefit.