Health secretary Andrew Lansley's overhaul of the NHS will take power away from doctors, the British Medical Association (BMA) has argued.
The government's plans centre on disbanding primary care trusts and replacing them with GP consortia - where the ability to purchase and commission services for patients would be placed in the hands of local doctors.
But the BMA, the UK's doctors' union, said that the power of the NHS commissioning board and the health secretary would be "overly restrictive and controlling".
Dr Laurence Buckman, chairman of the BMA's GPs committee, said the plans went against the government's pledge to devolve power to GPs.
"The NHS commissioning board will be given sweeping powers to get involved with the way consortia operate. Time and time again in the bill we see no mention of the need to consult consortia on matters that will have a direct and potentially very significant impact on the way they operate," he said.
The chairman demanded the bill include a clause requiring more consultation with the GP consortia.
"We are very concerned about how restrictive the bill is and want to see that, at the very least, there is a duty to consult consortia written into the legislation," Dr Buckman added.
"At the moment the secretary of state and the NHS commissioning board are being granted powers that are far too wide-ranging and seem to go against the promise to devolve power to local clinicians."
The BMA's worries are largely due to concerns that the NHS commissioning board will not be autonomous or "free from political control".
Under the health and social care bill, the NHS commissioning board will oversee the creation of GP consortia and hold the new groups of doctors to account for their commissioning and finances.
The doctors' union fears the board will dissolve and change consortia without consultation - and that the secretary of state will be able to impose conditions on consortia without the possibility of review.