Doctors' leaders claim NHS reforms aimed at giving GPs freedom to buy services for patients has clauses which may negate such pledges for change.
The Health and Social Care Bill clauses could prevent doctors from improving patient care, said the British Medical Association (BMA).
The new NHS Commissioning Board will not be able to operate autonomously and free from political control, and NHS reforms could see Health Secretary Andrew Lansley and the new board granted "overly restrictive and controlling" powers, said the BMA.
MPs are debating the Bill with a view to handing 80% of the NHS budget to family doctors, with doctors forming into groups known as "consortia" to work on commissioning services.
The union added that Mr Lansley would also be able to impose "any conditions on consortia without review" and the NHS Commissioning Board could dismiss a consortium's Accountable Officer and dissolve a consortia without consultation.
Dr Laurence Buckman, Chairman of the BMA's GPs committee, said: "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. And when it comes to the dissolution of a consortium, the most serious act of all, there is no requirement to consult the consortium or the public, and no recourse for appeal."
Dr Buckman said there were concerns about how restrictive the bill is. As it stands, Mr Lansley and the 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," he said.
Health Minister, Simon Burns, said: "This is nonsense. The bill gives GPs power to purchase and design services on behalf of their patients in a way that isn't possible at present."