Section 76A. The department shall have the general supervision of every affiliated company, as defined in section eighty-five, with respect to all relations, transactions and dealings, direct or indirect, with the gas or electric company with which it is affiliated, which affect the operations of such gas or electric company, and shall make all necessary examination and inquiries and keep itself informed as to such relations, transactions and dealings as have a bearing upon the price of gas or electricity supplied by such company or the quality thereof. Such relations, transactions and dealings, including any payments by a gas or electric company to such an affiliated company for services or materials and supplies which enter into the manufacture, distribution or sale of gas or electricity, shall be subject to review and investigation by the department in any proceeding brought under section ninety-three or ninety-four, and the department may order such affiliated company to be joined as a party respondent with such gas or electric company in such a proceeding.

Every affiliated company having such relations, transactions and dealings with the gas or electric company with which it is affiliated shall make such annual or periodic reports and in such form as the department may by regulation prescribe in order to give the department effective supervision over all such relations, transactions and dealings.

The supreme judicial court shall have jurisdiction in equity to enforce compliance with this section and with all orders of the department made under authority thereof.