Trusts are failing to respond to patient complaints adequately, a Healthcare Commission review has found.
Almost half of the 8,949 complaints reviewed in the year up to July 2008 were upheld or sent back to the trust for further work.
An equal proportion - 43 per cent - of complaints were about primary and secondary care, while 10 per cent were about mental health, 1 per cent strategic health authorities, 0.9 per cent ambulances and 0.8 per cent prisons.
The way trusts handle complaints is still the number one issue raised by complainants, accounting for 19 per cent of cases reviewed, up from 16 per cent last year.
Other common issues were:
delayed diagnosis or failure to diagnose a condition;
delays in accessing care.
'Small fraction of treatments'
NHS Confederation policy director Nigel Edwards said only a very small fraction of the total treatments led to complaints.
He said: "There were 350 million treatments performed by the NHS last year and out of all this activity just under 9,000 complaints were made, 2,700 of which were upheld by the Healthcare Commission.
He added: "When things do go wrong, it is important that the process of complaining does not compound the original complaint, or create new concerns."
From April, the Healthcare Commission will be disbanded but its successor the Care Quality Commission will not take on its complaints handling role.
Instead, complaints will be dealt with by trusts and, if complainants are still unhappy, the Health Service Ombudsman.
Patient Concern co-director Joyce Robins said it was "astonishing" that the changes would abolish the independent review stage carried out by the Healthcare Commission.
"We have been fielding the same type of complaints for the past 10 years.
"Nothing changes and nothing is likely to change as long as trusts sit as judge and jury on their own failings," she said.