Updated from 3:12 p.m. EST

Bank of America ( BAC) CEO Ken Lewis on Thursday faced a call for his ouster from a large institutional investor, who blamed "outsized, reckless risks" for severely undermining confidence in the company.

CtW Investment Group, which represents pension funds and affiliates with nearly $2 trillion in assets under management, sent a letter to lead director O. Temple Sloan, calling on the board to remove Lewis. CtW plans to campaign with other shareholders to vote against the re-election of Lewis, Sloan and Thomas Ryan, chair of the corporate governance committee, at an upcoming annual meeting.

CtW is an activist group that often pushes for leadership and operational changes, with the goal of increasing stock returns for the six million union members it represents. CtW funds and affiliated Taft-Hartley plans hold 116 million shares of Bank of America, whose market value has plunged over 90% over the past year.

Using those figures and closing share prices, the CtW investment was worth $4.36 billion last year, but just $416.4 million at Wednesday's close.

"I was just looking at a stock chart and the failure has been staggering," says William Atwood, executive director of the Illinois State Board of Investments. "When BofA and the banks were all doing well, the executives were very well compensated because of their leadership. Now BofA has lost a huge percentage of its value, and you have to hold them accountable for this historic failure."

Atwood oversees retirement funds for the state employees, judges and the general assembly, which include 1.6 million BofA shares. Those holdings have plummeted from $60.1 million to $5.7 million.

Of course Bank of America is not alone in its struggles, as its sector has lost trillions of dollars in market value amid the financial crisis. Citigroup ( C) shares succumbed to market pressure on Thursday, falling below $1. BofA and Wells Fargo ( WFC) were also under pressure amid news that Moody's may downgrade debt ratings on both firms.

"It's not surprising that they're angry and ready to rumble," Amy Borris, deputy director of the Council of Institutional Investors, says of pension-fund managers and the employees behind those funds. "They represent the patient capital of the U.S. financial markets .... and they've taken huge hits to their holdings."

In the letter to Sloan, CtW Executive Director William Patterson notes that the group expressed its concerns about risk management in February 2008. Representatives of the investment group met with Bank of America were assured that there was diligent board oversight and appropriate measures were put in place.

However, in light of the way Bank of America handled the acquisition of Merrill Lynch, CtW feels duped.

The group calls the acquisition "hastily arrang ed " and "ill considered," noting that Merrill's huge losses were not unveiled until the deal was about to close. At that point, CtW believes BofA should have walked away instead of accepting government funds to complete the transaction.

CtW cites Merrill's distribution of $4 billion in bonuses despite its staggering losses and the deal nearly falling apart, and the New York Attorney General Andrew Cuomo's investigation of the matter, as further evidence that due diligence was not properly performed.

"Removing Mr. Lewis is now a necessary prerequisite to restoring BAC's credibility with shareholders, regulators and the public," Patterson asserts.

Bank of America did not immediately respond to a request for comment.

BofA shares closed down 9.8% to $3.24.