Barr on Monday gave federal prosecutors the green light to pursue "substantial allegations" of voting irregularities before the results of the 2020 presidential election, which Fox News has projected Democrat Joe Biden has won, are certified next month, even though little evidence of fraud has been put forth.
"Attorney General Barr’s memo is both flawed and deeply disturbing," Nadler, D -N.Y., said in a statement on Tuesday. "It is unlikely to open new legal avenues for the Trump campaign, but speaks to Barr’s dangerous and irresponsible impulse to pander to the President’s worst instincts."
President Trump has filed several lawsuits in battleground states including Georgia, Nevada and Arizona, alleging that poll watchers were blocked from observing vote counts, and ballots cast after Election Day were counted towards the final tally, but has not presented evidence to support his claims.
Meanwhile, Biden's team forged ahead with efforts to set up a smooth transition to the White House, despite Trump's refusal to concede.
States have until Dec. 8 to resolve election disputes, including recounts and court contests over the results. Members of the Electoral College meet Dec. 14 to finalize the outcome.
Barr's memo has spurred controversy within the Justice Department as well, with some worried that his loyalty to Trump has caused him to take the unusual step to intervene in state election disputes.
Generally, Justice Department policy is “not to conduct overt investigations, including interviews with individual voters, until after the outcome of the election allegedly affected by the fraud is certified.”
On Monday night, the Justice Department’s top prosecutor for election crimes, Richard Pilger, said he would step down from that post in response to the attorney general’s memo, according to an email he sent to colleagues and obtained by The Associated Press. He is still expected to remain as an attorney within the Justice Department’s criminal division.
"The Attorney General may think that he is merely humoring a President who will eventually concede the race and transfer power to his successor," Nadler said. "This approach is as short-sighted as it is cynical and destructive."
Barr cannot change the outcome of the election, but conducting the investigation without evidence is threatening harm to the country, he said.
"One way or the other, Donald Trump will be out of office in a matter of weeks," Nadler said. "History will remember their conduct between now and then."
The Associated Press contributed to this report.