The number of complaints about hospital services in Hartlepool made to the national watchdog jumped sharply in the last year,
But new figures from the Parliamentary and Health Service Ombudsman show more reports were rejected than upheld.
The ombudsman received 43 complaints about North Tees and Hartlepool NHS Foundation Trust in 2014-15, up from 34 in the previous 12 months.
But just 13 of those complaints were actually accepted for investigation (down from 15 the previous year), of which five were upheld.
Six were rejected and the remainder were still under investigation at the end of the period in question.
A spokesperson trust for said: “When people are unhappy with any aspect of their care we encourage them to raise them straightaway because this gives us the opportunity to listen and try and put things right immediately.
“A proportion of the concerns and complaints we receive go on to become formal written complaints and, out of those, some patients or relatives who are not satisfied with our response refer us to the Parliamentary and Health Service Ombudsman.
“We have seen a very small rise in the number of complaints referred to and partly upheld by the Ombudsman. We take these issues extremely seriously and use any recommendations to improve our care and services for future patients.”
Ombudsman Julie Mellor said: “We are publishing this data to help trusts identify problems and take action to ensure trust in the system remains high.”