Nearly nine out of 10 (89%) doctors think increasing competition in the NHS will lead to services being fragmented, a poll has shown.
Some 65% believe competition between providers, including NHS and private companies, will reduce the quality of patient care, while 61% think the Government's reforms mean they will spend less time with patients.
The survey of British Medical Association (BMA) members was carried out by Ipsos Mori.
Overall, 18,456 BMA members in England were invited to complete an online survey and 1,645 responded - a response rate of 9%. Of those who replied, 66% said the proposal for GPs to lead commissioning of services will lead to even greater health inequalities.
Most doctors believe NHS reforms will lead to increased competition but only one on five think they will improve care.
Some 67% think closer working between GPs and hospitals would improve services for patients, but only 34% have faith the reforms will lead to this.
The King's Fund think-tank also published a new report saying market forces alone will not improve hospital services.
It said the Government's reforms of the NHS, with GPs in control of the budget, are unlikely to result in strong commissioning of services. Yet such commissioning is needed to reconfigure some services, including cancer, cardiac and stroke care across large geographical areas.
Shadow health secretary John Healey said: "David Cameron's been quick to say doctors will be the big winners from his NHS overhaul. But here we have further evidence that even most of them think it will damage patient care."
A Department of Health spokesman said: "Change is often met with apprehension. That's why we will continue to listen to doctors and to support them. But doing nothing is not an option. With growing demands on healthcare and outcomes, like cancer survival rates, amongst the worst in Europe, we need to modernise the NHS now."
