The number of written complaints received by frontline NHS trusts in England jumped by more than 5% during 2005-06.
Most complaints were about clinical care
Figures from the Information Centre for Health and Social Care show that 95,047 complaints were registered during the year.
This compared with 90,413 complaints made during the previous 12 months.
Three out of four were resolved locally by the hospital or community service within the target time of 20 days.
This is the same proportion as the previous year, but 10% higher than when records began in 1997-1998.
However, 21,755 complaints were not resolved within the target time, and nearly 2,000 had not been resolved at all by the time the data was collected.
In 2005/06, there were just over 36,000 complaints about aspects of clinical care.
Just under 11,500 complaints were about delays and cancellations of outpatient appointments.
And nearly 11,500 were about the attitude of NHS staff.
The number of complaints about family health services, such as GPs and dentists, has remained level at around 43,000 for the past three years.
The highest number of complaints were recorded in London (19,338), followed by the North West (12,560).
The North East region recorded the fewest number of complaints (3,940).
Three individual trusts recorded more than 1,000 complaints. They were:
- Leeds Teaching Hospitals NHS Trust
- University Hospitals of Leicester NHS Trust
- Barking, Havering and Redbridge Hospitals NHS Trust.
Health Minister Andy Burnham said the rise could be partly due to the fact that the Department of Health had been actively encouraging NHS organisations to welcome complaints in order to learn from them and improve services.
"We have long maintained that looking only at the number of complaints fails to tell the full story. What is more important is what action is taken in response to complaints.
"The Department of Health has already taken steps to improve the way complaints are handled in secondary care, and recent changes to the NHS Complaints regulations will support a better response to complaints."
But Liberal Democrat health spokesman Steve Webb said: "This is a further symptom of an NHS under pressure from weekly job cuts and service reductions.
"Front line staff need support to deliver a quality service, rather than the
government's constant reorganisation."