Doctors protect other doctors – even when they do wrong. That’s the conclusion of a study that found that nearly half of U.S. physicians do not report medical incompetence and mistakes by peers.

A survey of more than 1,600 physicians found that 45% with direct knowledge of incompetent members of their practice did not always report them. A total of 46% who knew of a serious medical error did not report it to authorities at least once. Those polled were doctors who specialize in anesthesiology, cardiology, family practice, internal medicine, pediatrics, and surgery.

“This raises serious questions about the ability of the medical profession to regulate itself,” noted Eric Campbell, associate professor at Harvard Medical School and the study’s lead author.

The New York-based Institute on Medicine as a Profession (IMAP), which is affiliated with Columbia University, conducted the survey. The survey appeared in the Dec. 4 issue of the Annals of Internal Medicine.