Wall Street’s main overseer is set to adopt new conflict-of-interest rules for brokers, a sweeping regulatory overhaul that has drawn criticism from investor advocates for being too lax, Bloomberg News reported. The measure, expected to be approved today by a divided U.S. Securities and Exchange Commission, will require brokers to act in the “best interest” of clients. What that actually means, however, remains in dispute, and the changes are unlikely to end a decade-long fight over the protections. SEC Chairman Jay Clayton has said the agency’s action will raise the bar for dealing with conflicts while leaving investors free to choose the type of financial professional that suits their needs. The rule -- which will affect tens of millions of investors who buy stocks and bonds to save for college, retirement and new homes -- has won widespread backing from financial firms.