The parties or either party to a controversy between employers and employes may invoke the services of the department, or the department may proffer its services in a controversy over the making, maintaining or the application of an agreement between employers and employes concerning wages, hours or conditions of employment. Whenever the services of the department have been invoked by any party to a controversy, or when the department has proffered its services, the department shall promptly put itself in communication with the parties to such controversy, and shall use its best efforts by mediation, through a representative of the Secretary of Labor and Industry, to bring them in agreement. Information disclosed by a party to a mediator in the performance of mediation functions shall not be divulged voluntarily or by compulsion. All files, records, reports, documents or other papers received or prepared by a mediator while serving as such shall be classified as confidential. The mediator shall not produce any confidential records of, or testify in regard to, any mediation conducted by him on behalf of any party in any type of civil proceeding.