There were 2,656 complaints about Surrey NHS services in the past year, as recorded by the Health and Social Care Information Centre.
But Healthwatch England concludes that 61 per cent of those who experience poor care, or witness a friend or relative receiving unacceptable treatment, do not report it.
The watchdog concludes that many are deterred from pursuing their grievance. This is because they either feel the complaints system is too complicated, that it takes too much effort or they have no faith it will make any difference.
Mike Rich, chief executive of Healthwatch Surrey, said: “The main reason people complain when they receive poor care is to save other people suffering the same in the future.
“Unfortunately the current system is making it very tough for people to make their voices heard.”
Of those people who contacted Healthwatch Surrey in the past 12 months, more than 45 per cent sought help making a complaint.
To contact the group, call 0303 303 0023 or visit www.healthwatchsurrey.co.uk