CtW Investment Group, an adviser to union pension funds holding about 0.15 percent of Wal-Mart’s shares, said an internal Wal-Mart memo released during shareholder litigation showed that Ernst & Young was informed by Wal-Mart’s internal audit services, or IAS, unit that a whistleblower had provided evidence of the alleged Mexico bribery scheme to Wal-Mart. “E&Y was briefed by IAS over the course of the Company’s internal investigation from late 2005 through early 2006,” according to a letter sent last week by CtW to the Public Company Accounting Oversight Board, or PCAOB.