Whenever a county legislative authority has approved by motion and certified all or part of a comprehensive plan, no road, square, park or other public ground or open space shall be acquired by dedication or otherwise and no public building or structure shall be constructed or authorized to be constructed in the area to which the comprehensive plan applies until its location, purpose and extent has been submitted to and reported upon by the planning agency. The report by the planning agency shall set forth the manner and the degree to which the proposed project does or does not conform to the objectives of the comprehensive plan. If final authority is vested by law in some governmental officer or body other than the county legislative authority, such officer or governmental body shall report the project to the planning agency and the planning agency shall render its report to such officer or governmental body. In both cases the report of the planning agency shall be advisory only. Failure of the planning agency to report on such matter so referred to it within forty days or such longer time as the county legislative authority or other governmental officer or body may indicate, shall be deemed to be approval.