The Secretary may act in the place and stead of a judge in any proceeding under this subpart. When he so acts the hearing clerk shall transmit the record to the Secretary at the expiration of the period provided for the filing of proposed findings of fact, conclusions and orders, and the Secretary shall thereupon, after due consideration of the record, issue his final decision in the proceeding: Provided, That he may issue a tentative decision in which event the parties shall be afforded an opportunity to file exceptions before the issuance of the final decision.