"I appreciate what Mr. Whitaker has done, but I think the time has come for new leadership at the department".
Barr's confirmation is expected in the Republican-controlled Senate, though his nomination encountered resistance Thursday from Democrats concerned by Barr's expansive views of executive authority and by his non-committal stance on making public Mueller's findings.
All 12 Republicans on the panel voted for Barr, while all 10 Democrats voted against him.
President Trump's pick to be the next attorney general is one step closer to be confirmed.
Sen. Amy Klobuchar (D-Minn.) said that Barr, as attorney general, would have the authority to change policies that now might prohibit him from revealing information about Mueller's work and that his nomination must be considered in the context of the historic moment in which the Justice Department finds itself.
Chairman Lindsey Graham, R-S.C., said before the vote that he begged Barr to get back into public service because he has the kind of experience the country needs at this time. Barr also defended a memo he sent to the Justice Department past year that was critical of the Russian Federation probe, explaining that it was narrow in scope and based on potentially incomplete information.
Barr has declined to offer a firm guarantee that he would release Mueller's report in its entirety - noting that the regulations governing Mueller's appointment do not call for that.
Chuck Grassley, an Iowa Republican, and Richard Blumenthal, Connecticut Democrat, introduced legislation requiring a special counsel to submit a report to Congress.
Barr, who ran the Justice Department from 1991 to 1993 during the George Bush administration, answered questions during his confirmation hearing last month that indicated he would bring a conservative approach to immigration, law enforcement and civil rights enforcement.
Democrats on the U.S. House of Representatives' Judiciary Committee on Thursday prepared a subpoena to compel Whitaker to testify on Friday, prompting him to say he will not appear unless the subpoena threat is lifted. "We are already seeing unsafe threats to the rule of law". His nomination will be headed to the Senate floor for a full vote.
Several other Republican lawmakers, in deciding to cast their votes for Barr, said he should release the special counsel findings to the fullest extent, while protecting national security secrets.
"I don't believe Mr. Mueller would be involved in a witch hunt", Barr said at his hearing.
Barr said he takes seriously the department regulations that say Mueller's report should be confidential. His confirmation is expected to draw a bitter partisan fight, especially given how Barr would oversee the special counsel investigation.