GP consortia lined up to take control of their local medical services have still not been told exactly which areas they will be responsible for.
Urgent clarification is needed, as is proper guidance, according to the NHS Alliance.
Dr Ken Aswani, of Waltham Forest Federated GP Consortium in London and executive member of the NHS Alliance, said the proposed changes "will cause initial confusion" for GP commissioners.
"There is an urgent need for rapid local education over the new structures and how they will work at local level as GP commissioning starts to get real," Dr Aswani said.
A report compiled by the alliance, entitled A Shared Agenda In The New World, points out that the Tory-Lib Dem coalition's proposals overlook the relationship between the public health system and GP consortia.
Health protection functions, such as vaccinations, are already causing confusion, it said.
The situation will get even worse once the Health Protection Agency merges with Public Health England, the report added.