President Trump on Wednesday escalated his criticism of a Justice Department official whose link to a controversial dossier of allegations about the Trump campaign has prompted scrutiny from the president and his allies in Congress, suggesting in a sharply worded tweet that the career civil servant should be fired.

“How the hell is Bruce Ohr still employed at the Justice Department? Disgraceful! Witch Hunt!” Trump wrote to his 54 million Twitter followers Wednesday morning.

Trump continued his criticism Wednesday night and Thursday morning. He tweeted that Chief Justice John G. Roberts Jr. should order the presiding judge of the Foreign Intelligence Surveillance Court, which vets national security wiretap requests, to question Ohr and other department officials about what he charges was the use of the dossier to “spy on the Trump campaign.” It is highly unusual for a president to instruct the judiciary to do his bidding. Hours later, Trump took aim at Ohr’s wife.

Ohr, who has spent more than 25 years at the Justice Department in relative anonymity, has in recent months drawn Trump’s ire because of his interactions with a longtime associate, Christopher Steele, a former MI6 operative whose probe of the alleged ties between Trump’s campaign and Russian officials has infuriated the president.

The president’s latest swipe at Ohr follows a threat earlier this month to revoke Ohr’s security clearance.

On Tuesday, Ohr was questioned in private for about eight hours by seven Republican lawmakers, members of the House Judiciary and Oversight panels. Much of the interview focused on Ohr’s association with Steele, as the members sought to substantiate their contention that Ohr and Steele, along with senior FBI and Justice Department officials, were engaged in an effort to derail the Trump campaign in 2016.

The members queried Ohr about his relationship with Fusion GPS, a research consulting firm that hired Steele in 2016. The firm also employed Ohr’s wife, Nellie Ohr, as a contractor.

“Wow, Nellie Ohr, Bruce Ohr’s wife, is a Russia expert who is fluent in Russian,” Trump tweeted Thursday morning. “She worked for Fusion GPS where she was paid a lot. Collusion! Bruce was a boss at the Department of Justice and is, unbelievably, still there!”

Steele produced a series of memos for Fusion GPS, loosely referred to as a “dossier,” outlining allegations about Trump’s activities in Moscow, including an unproven assertion that the Kremlin and Trump’s campaign team conspired to help Trump win the election. Special counsel Robert S. Mueller III is investigating that allegation as part of his probe of Russian interference in the election.

Although Steele’s information was used, it was not the only evidence authorities cited to obtain the warrant for Page, according to a redacted copy of the order released in July. Trump’s call for the chief justice to direct the surveillance court to investigate Ohr, whose job had nothing to do with preparing applications for national security wiretap orders, and other department officials is unprecedented, experts said.

“This reflects a lack of understanding and appreciation for the relationship between the presidency and the judicial branch, as well as the way the judiciary operates,” said Mary McCord, a former senior Justice Department official. “It’s not the role of the executive branch to give directions to the courts.”

Rep. Mark Meadows (R-N.C.) said Ohr told lawmakers he notified Justice Department and FBI peers at the time about the dossier’s reliance on hearsay and some witness bias against Trump, alerting Peter Strzok, then an FBI counterintelligence agent; Andrew McCabe, then the intelligence agency’s deputy director; and Andrew Weissmann, then chief of the Justice Department’s criminal fraud division.

But other individuals familiar with the Tuesday interview said Ohr explained that Steele’s “bias” stemmed from his concern that Trump was compromised by the Russians.

“Contrary to the allegations of several Republican members, Mr. Ohr’s testimony does not cast doubt on the credibility of the dossier,” the Democratic leaders of the Judiciary and Oversight committees, Reps. Jerrold Nadler (N.Y.) and Elijah E. Cummings (Md.), said in a statement.

“Like the four other interviews scheduled by the Republican Majority over the August break, yesterday’s interview seems to have been a complete waste of time in trying to prove what has already been thoroughly debunked,” the statement continues. “We learned little about Mr. Ohr that we did not already know. Mr. Ohr violated no law, regulation, or Department of Justice policy. Much of his career with the Department has focused on his work fighting Russian organized crime — which makes us wonder why House Republicans have now joined President Trump in focusing their energies on trying to fire Mr. Ohr without just cause.”

Trump’s tweet targeting Ohr is a clear signal “that Ohr is someone the president would like to be rid of,” said Donald Kettl, a professor of public affairs at the University of Texas at Austin. The attack seems linked to Ohr’s association with Steele and the dossier, an issue that causes Trump political embarrassment, Kettl said.

“This is a very big deal,” he said, “not only because it suggests political retribution, but it casts a chill and a shadow over this principle of merit, which has been at the core of government for far more than a century.”

The Justice Department declined to comment.

Ohr, 56, began his career in 1991 as a federal prosecutor in Manhattan and moved to Washington in 1999 as head of the Justice Department’s organized crime and racketeering section. In 2014, he was tapped to head the Organized Crime Drug Enforcement Task Force, which disburses grant money to law enforcement agencies to fight organized crime.

In December, as questions emerged about his relationship with Steele, Ohr was demoted within the task force to a job that did not entail interaction with the White House. In January, he was moved to a position as senior counsel in the Office of International Affairs.

Ohr told lawmakers that one reason for his reassignment was his failure to notify leadership, including then-Deputy Attorney General Sally Yates, of his interaction with Steele. Ohr said he kept FBI officials as high up as McCabe informed of his dealings with Steele. He had a dozen communications with Steele between late 2016 and May 2017.

The lawmakers pressed Ohr on why he remained in contact with Steele after Steele was dropped as an FBI source. Ohr told committee staff that there have been instances in which a former source was reintegrated into an investigation, according to people familiar with the session.

Ohr and Steele have known each other since at least 2007, when Steele was a top Russia expert working for the British intelligence community. When Steele began turning up information about Trump in 2016 that he believed the FBI should know, he contacted a bureau acquaintance who put him in touch with higher-ups. The FBI contracted Steele that summer to provide information about Russian efforts to interfere with the U.S. election. But months later, Steele, frustrated that the FBI seemed not to be acting on his tips, shared some of his findings with the media. The FBI severed its relationship with Steele.

During that period, Steele was also growing concerned that Republican lawmakers were seeking to expose his sources and asked Ohr to convey his concerns to the bureau.

Julie Tate contributed to this report.