The Healthcare Commission has rebuked 12 trusts for having a "significant lapse" in the way they handle patient complaints.
The organisation audited 42 trusts and found 10 had suitable systems in place. Of the remaining 32, 78% were told to make their complaints handling system more accessible.
Nine out of 10 had a significant lapse when it came to ensuring patients feel confident their care will not suffer because they have complained.
There is also "considerable variation" around the country on how trusts handle grievances, and managers should make it easier for people to raise complaints, it said.
Anna Walker, the Healthcare Commission's chief executive, said: "Given that the NHS provides 380 million treatments a year, the number of complaints - 140,000 - is relatively small.
"But when someone does complain, trusts need to respond well. Patients want complaints resolved quickly and locally.
"Trusts need to show they can respond to the individual's concern and learn as an organisation.
"If they do not, it could seriously damage people's faith in the NHS.
"The best organisations clearly value feedback from the people they serve, but the NHS is some way from doing this consistently."
Government proposals on how NHS complaints are handled are currently out to consultation.
The plans will strip the commission of responsibility for independently reviewing complaints, which would be dealt with by the Health Service Ombudsman.
Copyright © PA Business 2007
Take part in our short online survey and you could win one of four £25 M&S vouchers