Physicians are among the most trusted professionals in America, but a new survey shows that when it comes to dealing with colleagues’ mistakes or incompetence, many doctors abandon the high standards they espouse.

The first-of-its-kind survey of more than 1,600 physicians, published yesterday in the Annals of Internal Medicine, found that 45% said they did not always report an incompetent or impaired colleague to the appropriate authorities — even though 96% agreed that doctors should turn in such people.

Moreover, 46% said they had failed to report at least one serious medical error that they knew about, despite the fact that 93% of doctors said physicians should report all significant medical errors that they observe.

“We found large gaps between physicians’ espoused attitudes and what they do in actual practice,” the lead author and an assistant professor at Massachusetts General Hospital’s Institute for Health Policy, Eric Campbell, said.

“Failing to report incompetent physicians and allowing them to practice will have an impact on the welfare of patients,” Mr. Campbell added. “It’s clearly something that people should be aware of.”

The survey was conducted between November 2003 and June 2004 and funded by the nonprofit Institute on Medicine as a Profession, a think tank that promotes medical professionalism through a center at Columbia University.