Each utilities commissioner before entering upon the duties of his office shall file with the Secretary of State his oath of office to support the Constitution and laws of the United States and the Constitution and laws of the State of North Carolina, and to well and truly perform the duties of his said office as utilities commissioner, and that he is not the agent or attorney of any public utility, or an employee thereof, and that he has no interest in any public utility. (1933, c. 134, s. 5; 1935, c. 280; 1939, c. 404; 1941, c. 97; 1963, c. 1165, s. 1.)