The commissioner may call and hold hearings for any purpose deemed necessary by him for the performance of his duties. He shall hold hearings when required by the provisions of this chapter or upon a written demand therefor by a person aggrieved by any act or failure to act by the commissioner or by any rule, regulation or order of the commissioner. Such demand shall specify the grounds to be relied upon as a basis for the relief to be requested at such hearing and such hearing shall be held within forty-five days of receipt by the commissioner of written demand therefor, unless postponed to a later date by mutual agreement. The commissioner may in his discretion stay the effect of any order, rule or regulation pending hearing. The commissioner shall give at least fifteen days' notice of the time, place and matters to be considered at a hearing to all persons directly affected by such hearing. The commissioner shall allow any person directly affected by the hearing to appear in person and by counsel, to be present during the giving of all evidence, to have a reasonable opportunity to inspect all documentary evidence, to examine witnesses and present relevant evidence, and to have subpoenas issued by the commissioner to compel attendance of witnesses and production of evidence in his behalf. Formal rules of pleading or evidence need not be observed at any hearing. Upon written request seasonably made by a person directly affected by a hearing, and at such person's expense, or upon his own motion and expense, the commissioner shall cause a full stenographic record of the hearing to be made by a competent reporter. If further requested in writing by a person directly affected by such hearing, the commissioner shall cause such record to be transcribed and made a part of the official record of the hearing, at the expense of such person or may do so at his own motion and expense, and shall furnish a copy thereof to any party directly affected by such hearing at the request and expense of such party. Within forty-five days after completion of a hearing, unless the time be extended by mutual consent, the commissioner shall enter an order containing his findings of fact and conclusions upon the subject matter of such hearing. Such order may affirm, modify or nullify action theretofore taken or may prescribe new action within the scope of the notice of hearing, and a copy thereof shall be mailed to all persons directly affected by such hearing. In the discretion of the commissioner a rehearing may be granted to any party to a hearing upon written request filed with the commissioner within thirty days of the mailing of such order. Costs of any hearing or rehearing for the attendance of witnesses, service of subpoenas, and stenographic record and transcript may be taxed by the commissioner to any party or parties against whom he shall find and may be recovered in a civil action.