The majority of patients might suffer if only a small number complain about their GP under new rules for community surgeries, according to a doctors' representative at the British Medical Association (BMA).
He has criticised the GP Patient Survey, which will lead to practices being fined if they are subject to negative responses over waiting times for appointments.
Says Laurence Buckman, chairman of the BMA GPs' committee: "We are not defending people who are not very good, but a large number of practices in England will be adversely hit and in many cases unfairly hit.
"The penalties are going to range from tiny to huge. I don't think patients realised that when they filled in the survey. The results can be skewed enormously by responses from a small number of patients."
He was referring to new rules under which a practice of three GPs with 5,800 patients may lose £7,000, while a larger one may be £25,000 worse off.
It is claimed that this would in turn lead to cutbacks, including cutting staff hours and the number of appointments that would then be available.
Criticism was levelled at the survey itself on the grounds that although only two of 49 questions will affect GPs' funding, both are to do with appointments.