The federal regulator of mortgage finance giants Fannie Mae and Freddie Mac raised concerns on Tuesday about the Obama administration’s approach toward housing, questioning whether the government should continue to play a significant role in helping borrowers get home loans. Edward J. DeMarco, acting director of the Federal Housing Finance Agency, became the first major voice within the government to express reservations about the administration’s strategy for revamping the nation’s housing policy. “Recently there has been a growing call for some form of explicit federal insurance to be a part of the housing finance system of the future,” DeMarco says in prepared testimony, scheduled to be delivered before the House Financial Services Committee. “The potential costs and risks associated with such a framework have not yet been fully explored.”