Embattled Attorney General Jeff Sessions was a key proponent of prosecuting then-President Bill Clinton for allegedly lying under oath in 1999.
Sessions recused himself from any investigation into Russian meddling in the U.S. election on Thursday.
But he remains under fire for failing to disclose at his January confirmation hearing that he twice met with the Russian ambassador to the U.S. during last year's presidential campaign.
Dozens of Democrats — including House Minority leader Nancy Pelosi — have accused Sessions of lying under oath and called for his resignation.
Richard Painter, who served as the chief White House ethics lawyer for President George W. Bush from 2005 to 2007, also made his opinion clear on Twitter late Wednesday.
But Sessions was on the other side of the coin when Clinton was accused of perjury over statements he made regarding his relationship with Monica Lewinsky.
"I am concerned about a president under oath being alleged to have committed perjury," Sessions said on C-SPAN in 1999. "I hope he (Clinton) can rebut that and prove that did not happen. I hope he can show he did not commit obstruction of justice and that he can complete his term.
He added: "But there are serious allegations that that occurred. And in America, the Supreme Court and the American people believe that no one is above the law. The president has gotten himself into this fix that is very serious. I intend to give him an absolutely fair trial."
President Donald Trump said Thursday that Sessions could have been "more accurate" regarding testimony at his confirmation hearing but that he "did not say anything wrong."
Sessions has subsequently admitted that he met Russian ambassador Sergey Kislyak when a member of the Senate Armed Services Committee.
But he says the pair did not discuss anything to do with the presidential campaign, which he believed the questions put to him at his confirmation hearing were about.