(4)[ A person appointed under sub-section (1) to hold office as a Director or a person directed under sub-section (2) to hold office as an additional Director, shall not be required to hold any qualification shares nor his period of office shall be liable to determination by retirement of Directors by rotation; but any such Director or additional Director may be removed by the Central Government from his office at any time and another person may be appointed by that Government in his place to hold office as a Director or, as the case may be, an additional Director.