Labor Senator Sam Dastyari will confront the chief executives or deputies of Australia's largest banks with the personal stories of investors who lost money because of poor advice in a piece of political theatre designed to portray the opposition as sticking up for ordinary consumers against powerful financial interests. After being warned last week by Assistant Treasurer Josh Frydenberg not to use Tuesday's hearings by his Senate committee to conduct a "show trial" , Senator Dastyari - a former secretary of the NSW Labor Party and numbers man for leader Bill Shorten - will present four victims of financial advice in Parliament House ahead of the bank chiefs' appearance before his committee in the afternoon.