The King's Fund has warned that the fragmentation of commissioning means that there can be no single approach to combining health and social care.
The warning comes as NHS England and the Local Government Association host a meeting for the nine areas pioneering the combined funding approach.
The Integrated Personal Commissioning (IPC) programme began in April 2015 with over 10,000 gaining personal control of their health and social care budgets.
The nine areas are: Stockton on Tees; Barnsley; Cheshire West & Chester; Lincolnshire; Luton; Tower Hamlets; Hampshire; Portsmouth; and the South West Consortium.
The King's Fund analysed previous joint commissioning initiatives and warned that no approach could work everywhere.
The report, Options for integrated commissioning: Beyond Barker recommends that areas which can move quickly should do so from 2017 with all areas implementing the new arrangements by 2020.
The plans were originally laid out in the Barker Report, which was published in 2014.
Richard Humphries, assistant director of policy at The King's Fund, and the lead author of the report said: "As the Barker Commission set out, the case for change is overwhelming.
"Commissioning is more fragmented than ever, at a time when the imperative is to integrate around the needs of an ageing population with a mixture of conditions that defy service boundaries.
"Forty years of attempting to align health and social care leave us under no illusion about the difficulty of the journey to integrated commissioning, but with a consensus on the necessity of integrating care, there has never been a better time to make it happen."
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