Local authorities in around 20 parts of England have submitted bids to take control of health under devolution arrangements, according to MPs on the House of Commons communities and local government committee.
But a report by the committee warned that devolution plans 'had arrived at a difficult time' for the NHS, and should not be implemented in areas where it risked undermining existing integration.
The report said: 'Health devolution has arrived at a particularly difficult time for the health and social care system and its staff: there has been significant structural change in recent years and there is now an unprecedented level of financial challenge.
'With such uncertainty, we are concerned about the long-term consequences and recommend that, over an appropriate timescale, the government gathers evidence on the impact of these reforms. It is important that areas should not pursue formal health devolution at the expense of health and social care initiatives with similar aims that are proving fruitful. Areas that do wish to pursue health devolution must have clearly defined objectives for what they expect it to deliver.'
The report broadly accepted the case for devolution in Manchester, but MPs set out concerns that it may not be suitable for other areas.
The report warned that consultation had not been good enough over devolution plans in parts of England, and set out concerns over how pooled budgets would function and be audited. There was a lack of clarity over accountability for services delivered under devolved arrangements, it added.
'There is a need for a clear articulation of how health devolution will work and for clear governance arrangements set out in a way that residents, patients and staff can understand,' the report said. 'This will ensure there is no adverse impact on the quality of local services and that services are accountable. We are not satisfied that there has been sufficient consideration as to how pooled budgets will be regulated and audited and how they will be handled in practice.'