A federal judge in Washington, D.C., should consider recusing from Fusion GPS' subpoena fight against a Russian businessman, lawyers for the research firm told the judge last week.

Zuckerman Spaeder's William Taylor, Steven Salky and Rachel Cotton, who represent the research firm behind the so-called Russia Dossier, wrote in a letter to U.S. District Judge Trevor McFadden last week that he should consider whether to recuse from a case in which Fusion GPS is attempting to quash a subpoena. The letter was made public in a court order Monday.

The lawyers wrote that McFadden's impartiality could be questioned because of his work for President Donald Trump's transition team, his time as second in command at DOJ's Criminal Division and his representation of clients in private practice at Baker & McKenzie.

On Monday, McFadden issued an order welcoming briefing on whether he should recuse. The judge began work at the court in Washington, D.C., in November 2017, after he was nominated by Trump in June of last year and confirmed by the Senate on Oct. 30, 2017.

In the case, Fusion GPS seeks to quash a subpoena issued to the firm in connection with a lawsuit in federal court in Florida, where Russian businessman Aleksej Gubarev sued BuzzFeed for defamation after the news website published the dossier, which included claims about the Gubarev.

In the Jan. 3 letter, the Fusion GPS lawyers wrote that McFadden's work as a volunteer vetter on Trump's transition team last year raises questions. They cited Trump's tweets and statements about Fusion GPS during the time McFadden worked on the team, including a Jan. 11 tweet in which the president referred to the dossier as “a complete and total fabrication, utter nonsense.”

“Indeed, the President's adversity to Fusion GPS has been repeatedly expressed by his spokesperson and has become an element of his political agenda,” the letter said.

The lawyers added that McFadden should also consider any contributions, “financial or otherwise,” that he may have given to the Trump campaign. FEC data shows McFadden donated $1,000 to the Trump campaign in the 2016 election cycle.

The letter also cites McFadden's recent work at DOJ, where he was principal deputy assistant attorney general for the Criminal Division and oversaw the fraud section from January 2017 until his nomination. During that time, Sen. Charles Grassley, R-Iowa, sent a request to DOJ to investigate Fusion GPS for potential violations of the Foreign Agent Registration Act. The letter noted there was no reason to believe McFadden was involved in DOJ's reply to the senator but that other senior DOJ officials did testify before Congress on the matter.

Additionally, the letter raises concerns that McFadden, while in private practice as a partner at Baker & McKenzie, represented the company VimpelCom, now known as Veon, in an FCPA investigation. That company is controlled by Russian businessman Mikhail Fridman, who is also suing Fusion GPS for defamation in a separate case in the district court in D.C. It would be in Fridman's interest, the lawyers wrote, for the subpoena in the Gubarev case to be enforced.

In his order Monday, McFadden gave Fusion GPS until Jan. 15 to file a motion for recusal. Under federal law, judges should recuse in any matter in which “impartiality might reasonably be questioned.”