Former Treasury Secretary Robert Rubin has resigned as a senior counselor at Citigroup ( C) and will not stand for re-election to its board of directors, the company said in a statement Friday. Rubin has come under fire over the past two months for his role in encouraging the New York bank's foray into toxic debt that has laid waste to its balance sheet. The crisis of confidence in the bank led to a swoon in its share price late last year, before the federal government added $20 billion to the $25 billion preferred equity stake it had taken through the Troubled Assets Relief Program. The government also guaranteed $306 billion in illiquid assets against further losses. Rubin will remain a director until Citi's annual meeting. In the bank's statement, he said he intended to "deepen his involvement in outside activities and organizations to which he has been strongly committed." "This is not a decision that I have come to lightly," he said in the statement. "But as I enter my 70s and with all that is now in place at Citi, I believe the time has come for me to make these changes."