Private treatment centres harm the NHS and risk compromising patient care, even though they have helped cut waiting times, senior doctors say.
Cataract surgery is one of the operations carried out by treatment centres
The British Medical Association poll of 177 clinical directors in England found 68% felt the units, which treat NHS patients "destabilised" local services.
They were more positive about the 37 NHS surgery units, as they tended to be better integrated with hospitals.
But the government said use of private centres increased access and choice.
Treatment centres have been established by both the NHS and independent sector in recent years to drive down waiting times for minor surgery such as cataract operations.
The BMA survey found 70% of respondents thought patients had benefited from treatment centres, although the proportion was higher for the NHS than private units.
But they felt the centres could have a detrimental effect on the surrounding NHS.
None of the doctors questioned thought the private units had had a positive impact on services provided by their trusts, while nearly half said NHS centres had been of benefit.
Among the complaints made about private units were that they cherry-picked the less complex operations, meaning a loss of income for the local NHS and low staff morale.
Doctors also feared that future junior doctor training could be harmed if they were not given experience with minor surgery.
Two thirds also said they were aware of patients who had developed complications following treatment in the centres and needed readmission to their trusts.
When private treatment centres, the BMA called for better integration with existing service - many doctors said they had not been consulted on whether a unit was needed.
Doctors had reported of examples in Oxfordshire and Nottinghamshire where hospitals had resources standing idle because patients had to be channelled to treatment centres because contracts had been signed.
Dr Paul Miller, chairman of the BMA's consultants committee, said private treatment centres still had a role to play, but had to be better integrated.
"Without this, treatment centres risk compromising patient care as well as destabilising the local health economy."
And he said: "There is no problem with the NHS picking up the difficult cases, but these cost more and the health service should receive a higher tariff for them.
"If the NHS is not sufficiently paid for the work it does, it will simply go under."
But a Department of Health spokesman denied the units would harm patient care.
"We use the independent sector to provide services for NHS patients only where there are clear benefits for patients - either through faster access, increased choice, improved services, or better value for money for the taxpayer by raising productivity and innovation."