NEW: Trump impeachment witness accuses William Barr of arresting him to shield the president

Lev Parnas, a former business associate of Rudy Giuliani, made explosive allegations against outgoing Attorney General Bill Barr in a federal court filing on Tuesday. Parnas, who is under indictment for campaign finance violations and fraud charges, has accused Barr of timing his arrest last fall in order to prevent him from testifying at House impeachment hearings last fall.

The motion was filed in the Southern District of New York by attorneys for Parnas, a Ukrainian-born businessman who in 2018 and 2019 ran political errands in Ukraine on behalf of Giuliani and Trump. Parnas argues that his indictment last October was part of an intervention by Barr "to protect the President and thwart [Parnas'] potential testimony in the impeachment inquiry."

Parnas filed his complaint as reports broke that federal prosecutors in New York have discussed with Justice Department officials in Washington seeking a warrant for Giuliani's electronic communications, and, according to a person familiar with the case, at least one of the former New York mayor's cell phones. Approval from higher-ups at Justice is required before prosecutors may request a search warrant for any materials that may be protected by attorney-client privilege. It is unclear whether such approval has been granted in this case.

According to multiple reports and individuals familiar with the case, Giuliani's business dealings abroad have been part of a federal probe led by the FBI and the Southern District of New York — the very office Giuliani once led as U.S. attorney. Those investigations grew out of the arrest last October of Parnas and business partner Igor Fruman, who were detained at Dulles International Airport outside Washington as they waited to board an overseas flight. The two men were arrested just hours after meeting with Giuliani at the Trump International Hotel in Washington. According to the court filing, Giuliani was originally supposed to join Parnas and Fruman on their trip to Ukraine, but canceled earlier that day. Two other Giuliani associates also slated to make the trip had canceled a few days earlier, according to the document.

Prosecutors charged Parnas and Fruman, along with two other associates, with conspiring to make campaign donations on someone else's behalf and violating the federal prohibition on soliciting donations from foreign sources. A superseding indictment this September added fraud charges in connection with their company, Fraud Guarantee, which contracted with Giuliani to do promotional work. Giuliani has not been charged in connection with any aspect of the case. Parnas and Fruman have both pleaded not guilty.

In the new filing, Parnas lays out a series of events that he believes Barr helped engineer to secure his silence.

In late September, Parnas received a letter from House investigators asking him to preserve documents and prepare for a deposition. When Parnas told Giuliani about this, he was directed to attorney John Dowd, who had previously represented President Trump in connection with Robert Mueller's investigation of Paul Manafort, the former Trump campaign chair now serving time in prison. After securing the president's personal approval, Dowd took Parnas as a client.

On Oct. 8, a Tuesday, Dowd sent an email to a number of attorneys affiliated with Trump's defense team, calling the president "Boss" and promising that Dowd would "eliminate any doubt" that Parnas and Fruman would answer questions before Congress. Dowd then sent a letter to House investigators informing them that Parnas and Fruman would not appear for their scheduled deposition on Thursday, Oct. 10.

The next day, Parnas and Fruman were arrested. Two of the attorneys copied on Dowd's email were the same people who had been scheduled to fly with them to Europe. That night, Barr, who had been informed about the indictment in advance, met Fox News owner Rupert Murdoch for dinner in New York. The attorney general visited the Southern District offices the following morning on what aides described as a "routine" visit.

At the time of the arrest, however, the federal investigation into Parnas was not over, and did not in fact conclude for 11 more months, until a grand jury returned the fraud charges. It is not entirely clear why an immediate arrest was deemed necessary, although Parnas was described as a flight risk — on a trip the president's personal attorney was supposed to make with him.

Days after the arrest, Giuliani parted ways with his own attorney, Jon Sale, a prominent Miami lawyer Giuliani said he had retained for impeachment defense. Giuliani previously told Salon that Sale had been the person who first connected him with Parnas in 2018. He and Sale also shared a significant client: Venezuelan financier Alejandro Betancourt, who was under investigation in a multibillion-dollar money laundering probe and also knew Parnas.

Within a few weeks of these events, Parnas fired Dowd, after what he later described in a TV interview as a jailhouse loyalty shakedown.

"I called Dowd to come there. And I started seeing in the process of the bail stuff, the way things were going on ... I didn't feel they were trying to get me out," Parnas told MSNBC's Rachel Maddow in January. "John Dowd, instead of comforting me and trying to calm me down and telling me I'm going to be OK, he started talking to me like a drill sergeant."

"Were they telling you to sacrifice yourself to protect the president?" Maddow asked.

"That's the way I felt," Parnas replied. He dismissed Dowd along with Kevin Downing, another former Manafort attorney. In subsequent months, Parnas apparently turned over evidence to House impeachment investigators, but was never called to testify, likely because of his tarnished reputation following the arrest.

Parnas' motion seeks to convince the court to turn over numerous documents about the circumstances surrounding his investigation and arrest, as well as the investigation (or lack thereof) of other people associated with the Ukraine affair.

To make his case, Parnas must show that Barr improperly intervened in the indictment. His filing cites numerous instances of the attorney general improperly inserting himself on Trump's behalf in other legal matters, such as the cases of former national security adviser Michael Flynn, longtime Trump confidant Roger Stone and Trump sexual-assault accuser E. Jean Carroll. Parnas must also show that he and his associates were singled out for these campaign finance violations where others involved, such as the people who actually made the donations, were not.

The court filing quotes a voicemail Giuliani left with Parnas' attorney, the second half of which was apparently captured accidentally after Giuliani forgot to hang up. In the message, Giuliani asks whether it's possible to speak with or about Parnas, and leaves his number. After a pause, according to the transcript, Giuliani can be heard telling his attorney, who apparently was also present, "That's the soon-to-be-gotten-rid-of number." The two carry on a short conversation, then the voicemail ends.