By Louis Charbonneau, Nate Raymond and Michelle Nichols UNITED NATIONS (Reuters) - The United Nations' internal investigations office has uncovered serious lapses and due-diligence failures in the world body's interaction with organizations tied to an alleged bribery scheme involving a former U.N. General Assembly president. The 21-page confidential report by the U.N. Office of Internal Oversight Services' (OIOS), reviewed by Reuters, outlines the results of an audit ordered by Secretary-General Ban Ki-moon in response to charges against John Ashe, General Assembly president in 2013-2014, and six other people. The report gave the U.N. an overall grade of "partially satisfactory" in the March 22 report, which is available to U.N. member states on request.