The U.S. attorney in New York, Rudolph Giuliani, who made his mark as the chief prosecutor in Wall Street's historic insider trading scandal, has resigned, the Justice Department said Tuesday.

The resignation was expected since the well-known and highly visible official has been frequently mentioned as a possible candidate for mayor of New York.The Southern District of New York, for which he has been the U.S. attorney since 1983, also took the lead in investigating corruption in the New York City Parking Violations Bureau that led to the indictments and convictions of several top city officials and in major organized crime and narcotics cases.

In addition, Giuliani led the U.S. probe into the finances of exiled former Philippine president Ferdinand Marcos and his wife, Imelda, who have been accused of looting the Philippine treasury to secretly purchase prime Manhattan real estate.

The Justice Department said Giuliani would be replaced on an interim basis by Benito Romano, his former assistant and a partner at a New York law firm, Dewey, Balantine, Bushby, Palmer & Wood.