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In a withering rebuke of Attorney General William Barr, Sen. Mazie Hirono (D-Hawaii) on Wednesday demanded that the country’s top law enforcement official resign from his post amid what she decried as mounting evidence that he had participated in cover-up efforts on behalf of President Donald Trump.

The senator began her remarks, which came during Barr’s much-anticipated testimony on the Mueller report before the Senate Judiciary Committee, by disparagingly comparing Barr to Trump’s personal attorney Rudy Giuliani and White House counselor Kellyanne Conway—two figures, Hirono said, who have sacrificed their reputations in their work for “the grifter and liar who sits in the Oval Office.”

Hirono also directly accused Barr of lying to Congress, because he had told lawmakers that he was unaware of any potential concerns the special counsel had about his handling of the Mueller report. “Being attorney general of the United States is a sacred trust,” she continued. “You have betrayed that trust. America deserves better. You should resign.”

With her opening remarks completed, Hirono moved onto a fierce line of questioning about whether Barr believed it was appropriate for a president to ask his White House counsel to lie, questions that at times appeared to leave Barr visibly stumbling for answers.

Hirono was condemned by chairman Sen. Lindsey Graham (R-S.C.), who asserted that Hirono had not only excessively criticized the attorney general but “slandered this man from top to bottom.” Graham then turned to the next senator.