Any duly organized and existing trade association whether incorporated or not, is hereby authorized to institute and prosecute a suit or suits for injunctive relief and costs, provided by this act, as the real party in interest for and on behalf of one or more of the members of such association, when violation of this act directly or indirectly affects or threatens to affect or injure such member or members, or where violation of this act threatens or otherwise affects such member as provided therein.