Complaints about health and social care should be taken more seriously, says the Care Quality Commission regulator.
Its report said there was a wide variation in the way complaints were handled across the NHS, primary care and adult social care services in England.
Too often people were met with a "defensive culture", the report said.
Health Secretary Jeremy Hunt has welcomed the move to improve care and said progress had been made.
The CQC published its report after a review of the NHS complaints system a year ago by the MP Ann Clywd and nursing expert Prof Tricia Hart.
The report, Complaints Matter, looked at feedback and concerns the CQC received, its own inspection reports and information from providers, such as GP practices, care homes and hospitals.
It said: "We consider that much more could be done to encourage an open culture where concerns are welcomed, particularly as high numbers of providers in these sectors report that they receive very few or no complaints at all."
The report said people could be put off making complaints about care because providers were not willing to listen to concerns.
This could mean opportunities were being missed to improve the quality of care provided, it said.
Prof Sir Mike Richards, chief inspector of hospitals at the Care Quality Commission, who led the review, said while most providers had complaints systems in place, people's experiences of them were not consistently good.
"We know from the thousands of people who contact CQC every year that many people do not even get as far as making a complaint, as they are put off by the confusing system or worried about the impact that complaining might have on their or their loved ones' care.
"More needs to be done to encourage an open culture where concerns are welcomed and learned from."
The CQC says it has been looking at how to make complaints handling part of its inspections of health and adult care services in England.
This is to ensure that people receive care that is safe, effective and responsive to their needs.
Mr Hunt said: "As part of our drive to confront poor care we're making sure people know how to complain and transforming complaints handling - now a crucial part of the CQC's tough, independent inspection regime.
"Today's report shows both that that progress has been made and that there's still more to do."
Ms Clwyd said: "I welcome this report and in particular the CQC's intention to develop a thorough inspection regime for complaints systems in hospitals.
"I want the many thousands of people who wrote to me in the course of my review to know that change is expected as a result."