If NHS patients receive prompt apologies when mistakes are made it might reduce the number of complaints and legal actions, says the National Patient Safety Agency (NPSA).
But that goes against a culture in which "making a genuine apology after an error has occurred is a very hard thing to do for any clinician," says chief executive Martin Fletcher.
The NPSA runs a voluntary system under which trusts can report mistakes in an effort to learn from them and improve standards of care in the future.
It reports that in the last six months it dealt with nearly 500,000 cases, of which 5,700 were classed as serious - resulting either in death or permanent harm. Accidents and errors in treatment and medication were the most common.
The Action Against Medical Accidents patient group has said that "being open when things go wrong" is important when mistakes are made.