4The power of the tribunal to award costs or expenses shall include power to order a sum to be paid to the Postmaster General in respect of the expenses of the tribunal:
Provided that an order under this paragraph shall only be made where, in the opinion of the tribunal, the person against whom the order is made was acting frivolously or vexatiously in requiring the matter in question to be referred to the tribunal or, as the case may be, in making or resisting the application before the tribunal.