All agencies for relief, such as widows’ pensions, as provided by law, aid under the authority conferred upon the rehabilitation commission and public employment service, or other aids to relief, support or assistance, public or private, shall be made use of by the director of welfare and his subordinates and helpers, under the direction and supervision of the county welfare board to the end that causes of dependency on the part of persons or their families and the need for such public relief in whole or in part may be eliminated, and they are authorized under direction of the county welfare board to take such legal steps, either as prosecutors or petitioners in legal proceedings in aid of such persons or their families, as may be necessary to such end.