Almost two-thirds of appeals to the police watchdog over ignored complaints were upheld last year, figures have shown.
Forces "urgently need to examine their own practice to ensure that they are not blocking access to the complaints system", the Independent Police Complaints Commission (IPCC) said.
Some 1,374 appeals over a force's decision not to even record a complaint were made, up 16% from 2010/11, and almost two-thirds (61%) of these were upheld, with the watchdog telling forces to look at the complaints again.
Eight forces were told to reconsider complaints in three-quarters or more of appeals.
Overall, 6,339 appeals were made over complaints to police in 2011/12, up 3% from the previous year, with 38% of these upheld, up from 30% or less in the three preceding years.
In two forces, Northumbria and North Wales, more than half of appeals over complaints were upheld by the watchdog.
But the IPCC warned there was a wide variation between areas, with three forces upholding more than one in five complaints and seven upholding fewer than one in 10.
It also "still takes too long to resolve many complaints", IPCC chairwoman Dame Anne Owers said.
"It is of concern that not only has there been an increase in the number of appeals to the IPCC from those dissatisfied with the way their complaint was handled, there has also been a considerable increase in the proportion of appeals that we uphold," she said.
"All chief constables should take personal interest in the findings of this report and assure themselves that they and their staff are meeting their obligations to record and resolve valid complaints from the public.
"In particular, they should look closely at the number and type of appeals upheld by the IPCC."
The report's findings "suggest that complainants are facing barriers to accessing the complaints system when they had a valid complaint, and that too many investigations are failing to achieve resolution for the complainant first time".
The eight forces where 75% or more of the appeals over ignored complaints were upheld were: Bedfordshire (79%), City of London (75%), Cumbria (75%), Dorset (85%), Northumbria (76%), Nottinghamshire (82), Warwickshire (100%, where there was just one appeal) and West Yorkshire (76%).
The numbers of actual appeals were relatively small.
On the variation between forces, the figures showed Cheshire, Dyfed-Powys and Suffolk upheld more than one in five complaints while Cumbria, Greater Manchester, Humberside, Merseyside, the Metropolitan Police, South Wales and West Yorkshire upheld fewer than one in 10.
The Association of Chief Police Officers (Acpo) said policing was "public-facing and, as such, ensuring that our interactions meet with the standard expected is critical to maintaining public confidence".
Chief Constable Mike Cunningham, the Acpo lead for professional standards, said: "Officers have thousands of such interactions each day and most end well. Where there are instances of professional standards falling short, it's imperative to find out why and put it right.
"This report shows that the service can continue to improve, particularly in the initial recording of complaints to ensure that the system reflects the seriousness and value that police attach to the complaints process.
"The police service cannot continue to improve without feedback and we need the public to continue to come forward when they consider the service has fallen short."