A hearing examiner or agency member shall withdraw from any individual proceeding in which he cannot accord a fair and impartial hearing or consideration. Any party may request the disqualification of a hearing examiner or agency member, on the ground of his inability to give a fair and impartial hearing, by filing an affidavit, promptly upon discovery of the alleged disqualification, stating with particularity the grounds upon which it is claimed that a fair and impartial hearing cannot be accorded. The issue shall be determined promptly by the administrative head of the agency, or, if it affects a member or members of the agency, by the remaining members thereof, if a quorum. Upon the entry of an order of disqualification affecting a hearing examiner, the agency shall assign another in his stead or shall conduct the hearing itself. Upon the disqualification of a member of an agency, the agency shall proceed with the proceeding if a quorum remains. If a quorum no longer exists, by virtue of the member's disqualification, the Governor immediately shall appoint a member pro tempore to sit in place of the disqualified member in that proceeding. In further action, after the disqualification of a member of an agency, the provisions of Section 311 of this title shall apply.