A group of disgruntled former

Morgan Stanley

(MWD)

investment bankers aren't giving up their quest to wrest power from Phil Purcell, the CEO.

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In their latest salvo, the bankers released a letter calling for the Wall Street firm to spin off its investment banking unit, a move that would essentially undo the 1997 merger with the Dean Witter retail brokerage firm.

The eight dissidents seem determined to continue their highly public battle with Purcell, despite a series of rebukes from Morgan Stanley's board. Two weeks ago, the firm's board reaffirmed its support for Purcell.

The dissidents, who are also Morgan Stanley shareholders, have been calling for Purcell's ouster for months. The group contends the former Dean Witter executive has done damage to Morgan Stanley's reputation.

In the letter, the dissidents say that spinning off the firm's investment bank would allow the division to "regain its stature and reputation and significantly improve its performance."