Former White House national security adviser Michael Flynn on Wednesday demanded in a new court filing that Judge Emmett Sullivan recuse himself from "further participation" in his case, citing an "appearance of bias," which his legal team cast as "terrifying and mandates disqualification."

In a filing on Wednesday, Flynn and his legal team argued that Sullivan “cast an intolerable cloud of partiality over his subsequent judicial conduct” and “risked undermining the public’s confidence in the judicial process.”

OUTSIDE COUNSEL APPOINTED BY JUDGE IN FLYNN CASE URGES DOJ MOTION TO DISMISS THE CASE BE DENIED

“[A]ll that must be demonstrated to compel recusal,’ then, is ‘a showing of an appearance of bias …sufficient to permit the average citizen reasonably to question a judge’s impartiality, ” the filing states.

According to the filing: "The circumstances of this case lead any reasonable observer to believe that the current judge has a personal interest in the outcome, is irreparably biased against general Flynn, and is actively litigating against him. His continued presence in the case has become a national scandal undermining confidence in the impartiality of the federal judicial system and faith in the rule of law writ large. The Constitution compels, and all statutory bases require ('shall recuse'), that Judge Sullivan recuse himself from any further proceedings even if he has granted the motion to dismiss with prejudice.

“Judge Sullivan satisfied that standard when he actively litigated against General Flynn,” the filing continued. “He has since far exceeded it -- rising to the level of demonstrating actual bias.”

Flynn and his legal team added that “the court’s contempt and disdain for the defense was palpable throughout the hearing on September 29, 2020, including when defense counsel made an oral motion for his immediate disqualification, which he refused to allow even to be fully stated for the record.

”Accordingly, the defense files this motion to confirm the oral motion made at the hearing,” the filing stated. “Judge Sullivan’s Immediate Disqualification is Mandatory.”

"Judge Sullivan’s increasingly hostile and unprecedented words and deeds in what has become his own prosecution of General Flynn mandate his disqualification from further participation in these proceedings and the referral of his conduct to the D.C. Circuit Judicial Council," the filing continued. "The appearance of bias here is terrifying and mandates disqualification."

Flynn and his attorneys have for months been engaged in a back-and-forth with the D.C. Circuit Court of Appeals over the government’s efforts to dismiss the charges against Flynn of lying to federal prosecutors during the Mueller investigation about his contacts with a Russian ambassador. He recently changed his position, maintaining his innocence and seeking to withdraw that plea, while asserting that FBI agents acted improperly when they questioned him.

The Justice Department’s motion to dismiss raised such concerns about investigators' conduct. It came after unsealed FBI notes revealed that there had been a question regarding what the purpose of Flynn’s interview was: whether the aim was find out the truth or to get him to lie and thus subject him to being prosecuted or fired. Flynn ended up facing charges and being terminated from the national security adviser job.

When Attorney General Bill Barr moved to dismiss the charges against Flynn on grounds of prejudice, Judge Sullivan declined to rule on the motion.

FLYNN LAWYER IN FIERY HEARING TELLS JUDGE TO RECUSE SELF OVER 'ABJECT BIAS,' SAYS SHE ASKED TRUMP NOT TO PARDON

Flynn and his lawyers sought to bypass Sullivan, asking the D.C. Circuit Court of Appeals to issue a writ of mandamus — in this case, an order from a higher court to a lower court or official to fulfill their duties — to require Sullivan to grant the dismissal. In a court filing, Sullivan said mandamus is inappropriate at this stage because there remains the possibility he could still dismiss the case on his own.

Critics have claimed Sullivan has exhibited bias against Flynn in the yearslong case. In December 2018, the Clinton-appointed judge said the defendant “sold [his] country out.” Sullivan also controversially asked the prosecution whether Flynn should be charged with treason.

During a hearing last month, Powell claimed that Sullivan had displayed "abject bias" in the case and should recuse himself.

"Have you had discussions with the president about this case?" Sullivan asked Powell.

Powell at first tried to invoke executive privilege, but upon being reminded that she is not a federal employee, she acknowledged that she had.

"I can tell you I spoke one time with the president, one time about this case to inform him of the general status of the case," Powell said.

When asked if she had made any requests, she said, no, "other than he not issue a pardon."

Fox News' Bill Mears, Morgan Phillips and Ronn Blitzer contributed to this report.