The Royal College of GPs (RCGP) has rejected a claim by David Cameron that it "fully backs" health reform plans.
The Health and Social Care Bill has passed through the House of Commons stage with a margin of 65 votes.
It will now go to the House of Lords where it is expected to face further opposition.
During prime minister's questions, Mr Cameron claimed doctors and nurses – and in particular the RCGP and the Royal College of Nursing (RCN) – "fully backs" the bill.
Opposition leader Ed Miliband had told the prime minister that, in newspaper articles published this week, the British Medical Association, the Royal College of GPs and the Royal College of Midwives "all rejected your bill".
But in reply, Mr Cameron insisted that the RCGP and "the physicians, the nurses, people working in the health service [are] supporting the changes we're making".
In response to this remark, Dr Clare Gerada (pictured), RCGP Chair, said: "To reiterate our position; the college supports putting clinicians at the centre of planning health services.
"However, we continue to have a number of concerns about the government's reforms, issues which we believe may damage the NHS or limit the care we are able to provide for our patients.
"These concerns have been outlined and reiterated pre- and post-pause."
She went on to say the college is "extremely worried" about the reform as the current format may lead to an increase in damaging competition, increased costs and an increase in health inequalities.
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"Yes, lack of competition is killing the NHS. If the system is so good at it is, how come no other country has copied it in 63 years!" - Tina Chigbo, London
"NO!" - Puvan Markandoo, London