When the state tax commissioner is unable to perform any one or more of his public duties, through sickness, absence from his office, pressure of other public business, temporary inability to act or any other cause, and, from among any of the employees of the department under his supervision, he designates a deputy or a number of deputies to perform any or all of said duties in his stead and files a certificate with the secretary of state naming any such person as a deputy, then to the extent set forth in any such certificate, and for the period if any therein stated, any person so designated as a deputy may perform the duties imposed by law on the state tax commissioner until a revocation or modification of such certificate is so filed. The designation of any such employee as a deputy shall not affect or increase the salary received by him in his regular employment nor his rating or status in the state civil service.
N.J.S. § 54:1-11