Sanders, who was interviewed by Mueller's team as part of its investigation into Russian interference in the 2016 election, said that the claim was a "slip of the tongue."
On May 10, 2017, then-White House deputy press secretary Sarah Sanders told reporters that "countless" FBI agents had told the White House they had lost confidence in James Comey, who had been fired as FBI director the day before by President Donald Trump.
But special counsel Robert Mueller's report, released Thursday, shows that she simply made that up.
The report says Sanders, since promoted to White House press secretary, told investigators she had no evidence to make that claim.
Sanders, who was interviewed by Mueller's team as part of its investigation into Russian interference in the 2016 election, said that the claim was a "slip of the tongue." Sanders made the comment at a press conference one day after President Donald Trump fired Comey.
Sanders did not immediately respond to a request for comment.
The Mueller report underscored the extent to which the White House created an unreliable narrative about Comey's firing, with Sanders' statements deflecting questions about Trump's justification for the move.
"[Sanders] also recalled that her statement in a separate press interview that rank-and-file FBI agents had lost confidence in Comey was a comment she made 'in the heat of the moment' that was not founded on anything," the report stated.
Sanders told reporters at the 2017 press conference "the President, the Department of Justice, and bipartisan members of Congress had lost confidence in Comey," as did the rank and file of the FBI.
When a reporter indicated that the "vast majority" of FBI agents supported Comey, Sanders said, "Look, we've heard from countless members of the FBI that say very different things."
While Sanders' claim was widely scrutinized at the time, the revelation in the Mueller report that she admitted to having no evidence for the claim sparked renewed criticism.
"They all lie. Lie. Lie," tweeted Preet Bharara, a former U.S. attorney for New York's Southern District, on Thursday.
The report also details how Jeff Sessions, Trump's former attorney general, and Rod Rosenstein, the deputy attorney general, expressed concern to White House counsel Don McGahn about the White House's effort to push the narrative that Comey's firing was Rosenstein's decision.
McGahn later asked attorneys in the White House to work with the press to "correct the narrative." During an interview with NBC News anchor Lester Holt the day after the Sanders news conference, Trump admitted that he had made the decision to fire Comey because "of this Russia thing with Trump."