JPMorgan Chase & Co., the biggest U.S. bank, should oust most of its board and split Jamie Dimon’s dual roles as chairman and chief executive officer, shareholder advisory firm Glass Lewis & Co. said.

Stockholders should replace six of the board’s 11 directors at the bank’s annual meeting May 21 and approve a proposal to name an independent chairman, Glass Lewis said today in a report.

Calls for Dimon, 57, to relinquish the chairmanship have mounted since last May, when New York-based JPMorgan disclosed risk-control lapses in its chief investment office on credit- derivative bets that fueled a $6.2 billion trading loss and sparked regulatory probes. Institutional Shareholder Services on May 3 also urged a vote in favor of splitting Dimon’s roles and removing three directors.

Investigations by the company and lawmakers “have revealed questionable risk-management practices at both the senior management and board levels,” Glass Lewis wrote in the report. “Shareholders should be concerned that company management was allowed to build a massive exposure to credit derivatives,” switch risk models and undervalue its losses without triggering a review by the board.

Glass Lewis said shareholders should vote against James A. Bell, former chief financial officer at Boeing Co.; Crandall C. Bowles, chairman of Springs Industries Inc.; David M. Cote, CEO of Honeywell International Inc.; James S. Crown, president of Henry Crown & Co.; Ellen V. Futter, president of the American Museum of Natural History; and Laban P. Jackson, CEO of Clear Creek Properties Inc.

‘Well-Meaning Amateur’

“This is no longer a job for the well-meaning amateur,” Anne Simpson, a senior portfolio manager at the California Public Employees Retirement System, said on Bloomberg Television today.

Banking has become “fiendishly complex” and mistakes at institutions as large and complex as JPMorgan can threaten the health of the global economy, she said. “We really need people who can be on these boards not just to be rigorous and objective and tough as old boots, we actually really need them to know their business.”

Bell, Bowles and Jackson are members of the board’s audit committee. Cote, Crown and Futter serve on the risk-policy committee, which is responsible for oversight of risk-exposure management. The ISS recommendation said those three risk panelists should be voted out.

‘Too Willing’

“The risk-policy committee was likely too willing to trust senior management’s risk oversight and did not have meaningful review processes in place to cover instances of risk limit breaches or significant deviations in portfolio valuation,” Glass Lewis wrote in the report.

Both Glass Lewis and ISS endorsed a proposal in 2012 to split Dimon’s jobs and name an independent chairman, which was rejected by shareholders with 40 percent of the vote.

“With the two leading proxy advisory firms recommending investors vote against key directors, it is clear that the status quo can no longer continue,” said Dieter Waizenegger, executive director of the CtW Investment Group, which provides advice to union pension funds managing $250 billion in assets, including shares of JPMorgan.

Shares of the bank, which have gained 12 percent this year, climbed 2 percent to $49.14 at 2:26 p.m. in New York.

Buffett, Langone

The bank’s board urged shareholders in March to vote against naming a separate chairman, saying that Dimon’s dual role remains the “most effective leadership model.” He has since drawn public backing from billionaire investor Warren Buffett, who has said he personally holds stock in the bank, and Kenneth Langone, the billionaire founder of Home Depot Inc.

Last year’s losses in the chief investment office were the focus of a probe by the U.S. Senate Permanent Subcommittee on Investigations. The panel said in a March report that the bank dodged regulators and misled investors amid souring bets by trader Bruno Iksil, dubbed the London Whale because his positions were so big. Managers manipulated risk models and pressured traders to overvalue positions in an effort to hide mounting losses, according to the report.

While the bank acknowledged lapses relating to the CIO’s losses, an independent board committee found that mistakes weren’t attributable to the risk committee, Kristin Lemkau, a spokeswoman for the bank, said earlier this week.

Erik Gordon, a law and business professor at the University of Michigan in Ann Arbor, said Dimon “is the last in a line of imperial bank rulers.”

Dimon’s Ego

“The only reason to keep Dimon in both roles is to keep his ego intact,” Gordon said. “Vague claims by his friends on the board about it being the most effective model and threats of him leaving show how weak the governance is at JPMorgan.”

Investors would risk shortening Dimon’s tenure if they appoint a separate chairman and their company’s stock may lose its “premium valuation,” Charles Peabody, an analyst at Portales Partners LLC, said last month in a note to clients.

“This is not about personalities. Jamie Dimon is a hugely charming, intelligent, effective and charismatic individual,” said Simpson at Calpers, which held at least 10.7 million shares of JPMorgan as of Dec. 31, according to data compiled by Bloomberg. The board is supposed to “keep the CEO on the straight and narrow, so if the same person is doing both jobs, you simply do not have proper oversight,” she said.