Clinicians have warned that plans to allow foundation trusts to provide primary care services in England could create a conflict of interests among commissioners.
The plans would see hospital trusts compete with GPs and other providers to supply primary care services to PCTs.
Dr Michael Dixon, chairman of the NHS Alliance, said that foundation trusts would have a 'vested interest' in referring patients to their own hospitals.
'What better than to run primary services, and feed the beast of secondary care, making even more profit?' he said.
The plan was proposed by prime minister Gordon Brown in last week's wide-ranging speech on health policy.
He promised to 'increase the freedoms and autonomy of our local NHS' by 'giving hospital clinicians and GPs stronger incentives to work together and allowing foundation trusts the freedom to provide primary care services'.
Sue Slipman, director of the Foundation Trust Network umbrella body, said the new freedoms were 'very welcome'.
'Foundation trusts will be enthusiastic about using their expertise in this arena,' she added.
One trust which has expressed an interest in moving into primary care is University College London Hospitals (UCLH), which last year said it hoped to launch its own polyclinic.
Following Mr Brown's speech, UCLH chief executive Robert Naylor said that the trust would now consider providing services there itself, rather than outsourcing to GPs or a private provider.
Vertical integration such as this is permissible under the NHS Operating Framework for 2008/9, published last month.
However, the framework specifies that it should only happen where there are 'robust and proportionate safeguards and with the express agreement of the DoH'.
It also orders parties to the contract to declare conflicts of interest, and says clinicians must tell patients if they have a financial interest in a referral.
David Stout, director of the NHS Confederation's PCT Network, said that commissioners needed to be aware of conflicts.
Dr Dixon said that inviting acute trusts into primary care was 'very much a second best'.
'Foundation trusts don't know a great deal about primary care services because they're used to a linear model of secondary, disease-specific categories,' he said.
He added that the plan could improve services in areas where primary care was struggling.