Japan’s securities watchdog is planning to call for a bank and two brokerage firms under Mitsubishi UFJ Financial Group Inc. to be punished over allegations they shared confidential information about customer businesses despite being refused permission, a source familiar with the matter said Friday. The Securities and Exchange Surveillance Commission is considering recommending the Financial Services Agency take punitive action as early as next week against MUFG Bank, Mitsubishi UFJ Morgan Stanley Securities Co. and Morgan Stanley MUFG Securities Co. The two securities firms are alleged to hav…