JPMorgan Chase & Co. should name an independent chairman and oust three directors, a shareholder advisory firm said, boosting pressure on the bank to overhaul its corporate governance after a $6.2 billion trading loss.

Stockholders should vote in favor of a proposal to split the roles of chairman and chief executive officer, both currently held by Jamie Dimon, at New York-based JPMorgan's annual meeting May 21, Institutional Shareholder Services said in a report. ISS, which advises investors on proxy voting and corporate governance, cited "failures of stewardship" in opposing the re-election of three risk-committee directors.

Calls for Dimon, 57, to relinquish the chairmanship have mounted since last May when JPMorgan, the biggest U.S. bank by assets, disclosed risk-control lapses in its chief investment office on bets that fueled the trading loss and sparked regulatory probes. The May 3 ISS report could undermine the bank's efforts to persuade large investors to leave the leadership structure unchanged.