Criminal justice charity Clinks, drugs charity DrugScope, homelessness agencies umbrella body Homeless Link and mental health charity Mind have formed a coalition to support socially excluded and vulnerable adults.
The four organisations have launched a campaign, Making Every Adult Matter, to show that clients of their services often cross over and can fall between services.
Launching a report on the coalition's priorities, its members said the problems faced by adults with multiple needs would be researched and evidenced in order to influence policy in overlapping areas such as housing, drug and alcohol use, mental health problems and homelessness.
Research shows one in four prisoners leave prison without a settled address, about seven in 10 people seeking treatment for drug or alcohol problems have mental health problems, and 13 per cent of care leavers are homeless by age 19.
The coalition is supported by the Calouste Gulbenkian Foundation.