Allowing people to post comments about their GPs on an NHS website will be a "popularity contest" that may mislead patients, according to the British Medical Association (BMA).
It has accused the government of not thinking the plan through properly and allowing consumerism to dictate policy.
Laurence Buckman, chairman of the BMA's GPs committee, said: "A website on which people can slander or praise irresponsibly is the wrong approach.
"Patients should be able to choose a doctor, but I don't think this is the way to do it. It has a great potential to be misleading."
The Department of Health has said that remarks will be moderated to ensure nothing defamatory is included, and individual GPs will not be rated or identified.
A Department of Health spokesman said it is hoped that patients would be able to submit details about doctors' surgeries "by the end of the summer".
"NHS Choices provides a new way of communicating for the NHS, with an open dialogue between the patient, public and services," he said. "We are encouraging hospitals, and will do so with GP practices, to make the most of the patient comments facility to engage with patients.