Harvard Law School professor emeritus Alan Dershowitz said Deputy Attorney General Rod Rosenstein should limit special counsel Robert Mueller's investigation.
Dershowitz's comments came in an interview with CBS 11 in Dallas.
"I think Rod Rosenstein needs to say to the special counsel, 'Do not investigate the private finances of the president before he became president; do not investigate his relatives; do not investigate his sex life,'" Dershowitz said. "Don't do — to President (Donald) Trump — what Ken Starr did to President (Bill) Clinton."
"It started with Whitewater and ended up with a blue dress. That's not the appropriate way a special counsel should operate."
Dershowitz has maintained in the past that Mueller's investigation appears to be going beyond the scope of the original mandate.
Dershowitz told the television station that the appointment of special counsels is not the right approach.
"When you appoint a special counsel you give them targets and you say, 'You better get that guy or the people around him … and we're going to give you tens of millions of dollars. And if you come up empty handed you're a failure.'"
Meanwhile, Dershowitz believes the special counsel's probe should actually come to an end.
"I think the investigation should end and I think the Congress should appoint a special non-partisan commission," said Dershowitz.
"That's the way it's done in other western democracies," he said. "They don't appoint a special counsel and tell them to 'Get that guy …' That's what they did in the Soviet Union. Lavrentiy Beria, the head of the KGB said to (Joseph) Stalin, 'Show me the man, and I'll find you the crime!'" That's what (a) special counsel does."