The Secretary or his or her designee may, upon request, provide a claimant with legal assistance in processing a claim under the Act. Such assistance may be made available to a claimant in the discretion of the Solicitor of Labor or his or her designee at any time prior to or during the time in which the claim is being adjudicated and shall be furnished without charge to the claimant. Representation of a claimant in adjudicatory proceedings shall not be provided by the Department of Labor unless it is determined by the Solicitor of Labor that such representation is in the best interests of the black lung benefits program. In no event shall representation be provided to a claimant in a claim with respect to which the claimant's interests are adverse to those of the Secretary of Labor or the fund.