Veteran Belfast Ulster Unionist councillor Jim Rodgers has been handed a three-month partial suspension.
It follows an adjudication hearing by the Northern Ireland Local Government Commissioner for Standards, Marie Anderson.
The commissioner held, at a previous hearing on November 21, that Mr Rodgers had breached the Local Government Code of Conduct over a number of matters around failing to register or declare interests in organisations including Ashfield Girls High School and Belmont Bowling Club.
He has been suspended from membership of the East Belfast Area Working Group and the Strategic Policy and Resources Committee of Belfast City Council.
Announcing her decision, the commissioner found that Mr Rodgers has significant, non-pecuniary interests in both organisations, and that they ought to have been registered by him.
At the hearing held on December 5 to decide on sanction, the commissioner imposed a partial suspension on Mr Rodgers, preventing him from membership of the East Belfast Area Working Group, and the council's Strategic Policy and Resources Committee for a period of three months.
The commissioner commented that but for his exemplary record of public service, she would have imposed a full suspension.
The partial suspension has no impact on Mr Rodgers' other roles within the council.
Mr Rodgers has been an elected councillor since 1993 and has served twice as Lord Mayor of Belfast.