Washington — Some 2,000 former Justice Department officials who served in Republican and Democratic administrations are urging Attorney General William Barr to resign after the department intervened in the case of Roger Stone, a longtime ally of President Trump's, triggering claims of political interference.

The Justice Department alumni made their request to Barr in an open letter published Sunday and said the move by top officials at the department to overrule federal prosecutors in Stone's case was "unheard of."

Initially, some 1,100 signed on but that number almost doubled, hitting 2,003 during the day Monday.

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"Such behavior is a grave threat to the fair administration of justice," the former officials wrote. "In this nation, we are all equal before the law. A person should not be given special treatment in a criminal prosecution because they are a close political ally of the president. Governments that use the enormous power of law enforcement to punish their enemies and reward their allies are not constitutional republics; they are autocracies."

The Justice Department declined to comment on the letter on Monday.

The crisis of confidence that has ensnared the Justice Department reached a fever pitch last week after Barr overruled federal prosecutors who recommended Stone receive seven to nine years in prison for his November conviction on seven charges. The intervention led four prosecutors to abruptly withdraw from the case, and one resigned from the department altogether.

The Justice Department's move in Stone's case raised questions of whether the department was responding to political pressure from the White House, given that President Trump tweeted his displeasure with the initial recommended sentence and has repeatedly said Stone was unfairly prosecuted.

But in an interview with ABC News, Barr said Mr. Trump has never asked him "to do anything in a criminal case." He also denounced the president's tweets on pending Justice Department cases in a rare rebuke of Mr. Trump's actions, saying they "make it impossible for me to do my job."

Still, scrutiny over Barr heightened further Friday after the revelation that he assigned an outside prosecutor to review the work of prosecutors in the case of Michael Flynn, Mr. Trump's former national security adviser. This is not the first time Barr has tapped outside prosecutors to examine high-profile cases that have earned the ire of the president.

The more than 1,000 former Justice Department officials denounced Barr and the president's "interference in the fair administration of justice" and accused the attorney general of "doing the president's bidding."

"Those actions, and the damage they have done to the Department of Justice's reputation for integrity and the rule of law, require Mr. Barr to resign," they wrote. "But because we have little expectation he will do so, it falls to the Department's career officials to take appropriate action to uphold their oaths of office and defend nonpartisan, apolitical justice."

The officials urged Justice Department employees who witness misconduct to report the abuse, refuse to carry out directives that are contrary to their oaths of office, withdraw from cases or resign and make public their reasons for doing so.

"We likewise call on the other branches of government to protect from retaliation those employees who uphold their oaths in the face of unlawful directives," the former employees wrote. "The rule of law and the survival of our Republic demand nothing less."

Barr is scheduled to testify before the House Judiciary Committee on March 31, during which he is expected to be pressed about Stone's case and other issues.

Clare Hymes contributed reporting.