The Council or a board with the approval of the Council may appoint one or more committees to carry out, on behalf of the Council or board, such of the functions of the Council or board as that body may determine and as are not required in the case of a board to be carried out by an investigating or disciplinary committee.

A committee appointed under this paragraph shall consist of the number of members determined by the body appointing it, and not more than one third of the members may be persons who are not members of that body; and a member of such a committee shall hold office in accordance with the terms of the instrument under which he is appointed.