The state attorney general is calling for the resignation of University of Massachusetts President William M. Bulger (search), saying his decision to defend his fugitive brother calls into question his ability to run the state university system.

"You can go down one path or the other, but you can't go down both," state Attorney General Thomas Reilly said in an interview published Monday in the Boston Herald. "He made a choice to defend his brother, to counsel his brother, to advise his brother."

He said that action conflicts with running a university, "whose very mission is the pursuit of knowledge and truth."

James "Whitey" Bulger, a reputed member of the New England Mob who also was an FBI (search) informant, disappeared in 1995 just before he was to be indicted on federal racketeering charges.

In grand jury testimony two years ago, William Bulger -- a former state Senate president hired to run the university in 1996 ---- said he had no idea where his brother was, and spoke to him only once when he called shortly after he disappeared asking for legal advice. He has said he didn't feel obligated to alert authorities to "a private conversation."

Bulger is preparing to testify under a grant of immunity before a congressional committee investigating the FBI's handling of mob informants. Appearing before the same committee in December, Bulger invoked the Fifth Amendment (search).

On Monday, he called the attorney general's comments "irresponsible" and "a gross distortion of the facts."

"Changing the course of my brother's life is something I tried to effectuate for many years," Bulger said in a statement Monday. "That I was not successful is a matter of great personal pain."

He said he had always tried "to pursue my public responsibilities and to work for the public good."

Reilly said he agreed William Bulger was in a difficult situation, "but if it was my brother, and I made the same decision he's made ... as attorney general, I'd have to find another job."

Republican Gov. Mitt Romney, who also has criticized Bulger -- and proposed eliminating his UMass job as a cost-saving measure -- said Monday he would reserve judgment on Bulger's fitness to serve.

"I will await any comments about his moral authority to lead the University of Massachusetts until I hear testimony which is open to the public," Romney said.

No date has been set for the upcoming congressional hearing.