Some 41 complaints made against Norfolk County Council were upheld by the authority's ombudsman, with some cases costing thousand of pounds in pay outs.
The Local Government and Social Care Ombudsman received 150 complaints regarding the council during the year ending March 31 2018, compared with 125 the year before.
Of the 61 complaints that were investigated by the ombudsman, the council was found to be at fault in 67pc of cases.
Some of the complaints upheld include children missing up to two years of education and a man being banned from visiting his sister in care.
In the previous year, the ombudsman upheld 75pc of complaints - 33 of the 44 which went to investigation.
The ombudsman recognised that improvements were being made when it found the council had in 97pc of cases implemented its recommendations, with around 20 service improvements made between 2018-19.
A Norfolk County Council spokesman said: "We recognise that we could have done better.
"We are pleased that the ombudsman did acknowledge that certain complaints are very complex and they applaud us for working positively to fix them.
"To improve further we are providing additional training for staff and are seeking to work closely with the ombudsman to improve future outcomes."
An annual review of the ombudsman's local government complaints reveals the majority were related to adult social care and children's services. In some of those cases, the council paid out thousands in compensation.
In January, a mother complained the council did not provide her son, who has special educational needs, with suitable education for nearly two years. The council agreed to pay the family £4,000 to acknowledge the delay.
In another case, a family was paid £3,500 in compensation after the council failed to put provisions in place for a primary school-aged boy who missed eight months of education after being expelled. The council also paid the mother £400 after she paid for a dyslexia report.
In an upheld complaint reported in March, the council failed to provide adequate support to foster carers and ended a placement without notice, causing them financial loss. The ombudsman recommended the council pay an undisclosed amount for the distress caused.
Have you made a complaint that was upheld by the ombudsman? Contact Taz Ali on 01603 772531 or email taz.ali@archant.co.uk
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