Relentless organisational change and high staff turnover have left many health authorities unable to implement the government's public health agenda, according to a major study.
By contrast, primary care groups in some areas are seizing the initiative, with GPs willing and able to tackle health inequalities through inter- agency working.
The study, which examined 50 PCGs and their health authorities, confounds assumptions that it is GPs who are most nervous about taking on a wider role in improving health.
Geoff Meads, professor of health services development at City University, London, who led the Health Education Authority sponsored study, said he was surprised and encouraged by the commitment of GPs to public health.
'On the HA side there are some real dilemmas,' he said. 'The impact of continuous structural and organisational change has left them very insecure about where they should place their future commitment. Is the key relationship going to be with PCGs or unitary authorities? Should they be thinking larger or smaller?'
The ability of HAs to act strategically was hampered by their own lack of cohesion and continuity, he said. One HA was operating from five sites; at another the average job lasted for 18 months and was filled by the same person for only nine months.
The study identified four types of primary care organisation currently working in the NHS. Worryingly, only one had 'the capacity to take on public health', said Professor Meads.
That type is described in the report as a 'mixed-status public utility' - such as a highly developed PCG - in control of most healthcare resources and seeking a health 'dividend'.
Dr Chris James, chair of Southampton City PCG which featured in the report, emphasised the speed with which GPs are embracing their new role.
'We are working together as a team of primary care providers rather than as individual GPs,' he said.
'A few months ago when PCGs were putting together their views they were seen by HAs as the views of GP practices rather than as multi-agency views - and, really, we are multi-agency organisations now.'
But he added that public health expertise from health authorities was still essential, and he admitted that a public health role did not come naturally to GPs.
Mixing Oil and Water: how can primary care organisations improve health as well as deliver effective health care? Health Education Authority, Trevelyan House, 30 Great Peter Street, London SW1P 2HW. Free.