Doctors have accused the government of trying to privatise general practice after it published guidance about setting up new practices in England.
The government wants to improve access to GP care
Ministers have ordered health chiefs to create 100 GP surgeries and 150 super-surgeries known as polyclinics.
The British Medical Association said the guidance works against existing GPs from bidding for the contracts, leaving the field open for private firms.
But the government said all providers could bid for the contracts.
Ministers are known to be keen to get the private sector involved in GP care to widen access to services.
While health firms are heavily involved in hospital care - one in 10 NHS operations are by private providers - they have traditionally had a much more limited role in family doctor services.
Health chiefs working for primary care trusts (PCTs) have already been sent the procurement framework by the Department of Health.
The document sets out how PCTs should go about signing deals for new GP services next year.
The 100 surgeries are aimed at the most deprived areas.
And the polyclinics, which are health centres which house GPs alongside other services such as social care, nurses and some hospital services, are to be created across the country.
The BMA has reacted angrily to the framework saying it suggested health bosses should use the only GP contract, APMS, which allowed the private sector to bid for services.
The other two GP contracts, under which the overwhelming majority of current family doctors are delivering care, are not open to the private sector.
Dr Richard Vautrey, deputy chairman of the BMA's GPs committee, said it meant that many existing GPs could not bid to extend their current surgeries as they were operating on a different contract.
"Instead, they will have to put forward plans for completely new practices.
"That seems unfair and basically this is a way to get the private sector into the profession."
The latest row comes after the BMA could not agree a deal last week with government to get existing NHS GPs to work longer hours.
But a Department of Health spokeswoman said all providers would be free to bid for the new services.
"We are determined to address long-standing inequities in access to GP services. APMS can provide an additional lever to make the changes needed to tackle these health inequalities.
"We have asked PCTs to undertake open and transparent procurements, and we expect that they will typically use the APMS contracting route to do this."