Open this photo in gallery: A man walks past the Asian Infrastructure Investment Bank headquarters in Beijing on June 15.JADE GAO/AFP/Getty Images Former employees of the Asian Infrastructure Investment Bank have come forward to publicly challenge ex-communication chief Bob Pickard’s criticism of the institution as an instrument of Beijing that is dominated by China’s ruling Communist Party. Three ex-staffers told The Globe and Mail that they did not detect undue influence exercised by the Communist Party over the multilateral development bank that Mr. Pickard, a Canadian PR executive, has alleged in interviews and social-media posts. Mr. Pickard’s public split with...