Hampshire County Council was the subject of almost 150 complaints and enquiries to the ombudsman about its actions last year, new figures show.
The Local Government and Social Care Ombudsman is responsible for investigating wrongdoing in local public services.
If it finds that the council has acted in an unfair or unjust way, the ombudsman will offer recommendations on how to make things right.
According to figures from the body, there were 144 complaints or enquiries made about Hampshire County Council in the year to March – up from 115 the year before.
After investigation, the ombudsman found the council to have acted unjustly on 35 occasions last year.
The most common reason for coming to the ombudsman in Hampshire was for issues related to education and children's services, with 81 complaints or enquiries.
Michael King, Local Government and Social Care Ombudsman, said: "One complaint can have immense power to change things for the better.
“The vast majority of councils agree to the recommendations we make and see them as common-sense ways of providing better services for people in their area."
Across England, councils were found to have acted unjustly on 2,678 occasions, a 27% increase on 2,104 the year before.
He said that while councils act on nearly every recommendation they are given, uptake can be slow, with one in five failing to take them on within the timeframe set out by the Ombudsman.
Nationally, the number of complaints rose compared to last year, with 15,826 in the year to March, up 25% from 11,830 last year, but did not quite reach the 17,019 recorded in 2019-20.
Problems with education and children's services were the most common reason to get in touch with the organisation, with 3,145 complaints and enquiries, while there were more than 2,000 each for planning and development, adult social care, and housing.
Healthwatch England, a health and social care champion, said they were particularly concerned about the national rise in complaints about adult social care, suggesting that financial pressures may be to blame.
Jacob Lant, the charity's head of policy, said “At the heart of every one of these complaints is someone who relies on social care to help them live their lives, and by speaking up these people and their carers have tried to send a message about how services are not meeting their needs."
The number of issues raised about the sector rose from 1,670 in 2020-21 to 2,139 in the year to March – including 32 in Hampshire.
The Local Government Association meanwhile praised councils for the work they are doing in tricky circumstances.
Peter Fleming, chairman of the organisation's improvement and innovation board said: "Councils continue to deliver the crucial services that communities rely on, while also managing the ongoing cost-of-living crisis and the challenges it brings to their areas.
"It is positive that in 99.7% of case councils are implementing recommendations made, showing that local authorities are determined to make sure these issues do not occur again."