The embattled president of the University of Massachusetts system said that he would keep fighting for his job after the state's attorney general called for his resignation for refusing to cooperate with federal authorities trying to track down his fugitive brother. Just last month, the president, William M. Bulger, successfully quashed an effort by the governor to eliminate his position.

The comments from the attorney general, Thomas F. Reilly, surprised college officials and politicians in Massachusetts because he is a Democrat, like Mr. Bulger. Before taking over as president of the university system in 1995, Mr. Bulger was president of the State Senate for 17 years. Until now, efforts to oust Mr. Bulger have been led by the state's Republican governor, Mitt Romney.

In a news conference on Monday, Mr. Reilly said that Mr. Bulger was not fit to lead a university whose mission is "truth and knowledge." Mr. Bulger's brother, James (Whitey) Bulger, is one of the FBI's 10 most-wanted fugitives and is charged with 21 murders. Last December, William Bulger refused to testify before a Congressional panel that is investigating his brother, although he has since agreed to talk with the committee in a few weeks after lawmakers promised him immunity.

"When you will not lift a finger to help assist an investigation, when everything that comes from you has to be forced out of you, when you have to be compelled to do everything, you have made a choice," Mr. Reilly said. "And that choice, in my mind, is the opposite of what the mission of a university is."

Although Mr. Bulger has rarely discussed his brother in public, Mr. Reilly's comments prompted him to hold a news conference at his office on Monday. Reading from a prepared statement, Mr. Bulger said that he had tried with little success to get his brother to change his life. He called the statements by Mr. Reilly, who is expected to run for governor in 2006, an effort to "extract political advantage from something that is so personal and painful."

Mr. Reilly "is profoundly wrong when he suggests that I have ever taken steps that were at odds with my public responsibilities," Mr. Bulger said. "My public responsibilities have always come first."