WASHINGTON --- A leading Republican U.S. senator has called for deeper Justice Department investigations into the Washington lobbying firm connected to the explosive dossier compiled on President Donald Trump during last year’s election campaign and the firm’s alleged Russian ties.



The focus of the March 31 letter, from Chuck Grassley, the chairman of the Senate Judiciary Committee, is Fusion GPS and the work it did in particular connected to the human rights law passed last year known as the Global Magnitsky Act.



The letter, addressed to Acting Deputy Attorney General Dana Boente, targets the work Fusion did in 2015 and 2016 connected to the act, which had been introduced in Congress but at the time not yet voted on.



The letter cites from a complaint filed by British-American businessman William Browder that alleged Fusion GPS, a public relations firm founded by a former Wall Street Journal reporter, may have worked as a lobbyist "for Russian interests in a campaign to oppose the pending Global Magnitsky Act [and] failed to register under [U.S. law]."



"The issue is of particular concern to the committee given that when Fusion GPS reportedly was acting as an unregistered agent of Russian interests, it appears to have been simultaneously overseeing the creation of the unsubstantiated dossier of allegations of a conspiracy between the Trump campaign and the Russians," the letter said.

Fusion GPS surfaced in the public eye earlier this year when a report compiled by a former British intelligence officer about Trump’s business dealings in Russia emerged. The report, which was published in full by BuzzFeed, contained salacious and damning allegations about Trump, was reportedly commissioned by Fusion GPS initially for Trump’s Republican opponents, but then was acquired by Democratic operatives.

The Grassley letter highlights the work done by a Russian-American man named Rinat Akhmetshin, who was instrumental in the Washington premiere of a film that sought to undermine the narrative surrounding the Magnitsky law’s namesake, Russian whistle-blower Sergei Magnitsky.

Barely showing up in U.S. lobbying records, the 48-year-old Akhmetshin cut a low profile in Washington lobbying circles, even as he was tied to such efforts as bolstering opponents of Kazakhstan's ruling regime; discrediting a fugitive former member of Russia's parliament; and undermining a Russian-owned mining firm involved in a billion-dollar lawsuit with company information allegedly stolen by hackers.

Asked to comment on the allegations in the Grassley letter, Fusion GPS said in an e-mail to RFE/RL: "Fusion GPS was working for the U.S. law firm of Baker Hostetler, at its direction, in a litigation support role. That work is a matter of public record. By the very nature of that work, Fusion GPS was working with a law firm to ensure compliance with the law. Fusion GPS was not required to register under the Foreign Agents Registration Act."



Akhmetshin did not respond immediately to an e-mail seeking comment.



For his part, Browder is a London-based businessman who invested millions in Russia before being forced to leave the country in the mid-2000s. After the Russian companies he founded began to see unusual financial activity, Browder hired Sergei Magnitsky to investigate.



According to U.S. federal court records, Magnitsky then uncovered what appeared to be an audacious tax fraud scheme that stole $230 million from the Russian treasury. Magnitsky was later imprisoned by Russian authorities, accused of committing the same fraud he reportedly uncovered.



He died in a Moscow prison in 2009, suffering from ill health and, his supporters say, after being tortured. Three years later, after lobbying from Browder, the U.S. Congress passed the original Magnitsky Act, which sanctioned people allegedly connected to Magnitsky’s death, the underlying tax fraud, and other human rights abuses.



Last year, as Congress was considering passing new legislation that would expand the authority of the president to sanction rights abusers anywhere in the world, a film was screened in Washington that cast doubt on the narrative surrounding Magnitsky, insinuating instead that he was an accomplice in the tax fraud that was orchestrated by Browder.



The film, by Russian filmmaker named Andrei Nekrasov, was screened at the Newseum, at an event organized by Akhmetshin.



"It is particularly disturbing that Mr. Akhmetshin and Fusion GPS were working together on this pro-Russia lobbying effort in 2016 in light of Mr. Akhmetshin’s history and reputation," the letter from Senator Grassley said.



By tying Fusion to Akhmetshin’s work, Grassley appeared to be also trying to undermine the salacious dossier, which Trump has repeatedly and resoundingly denied.



"As you know, Fusion GPS is the company behind the creation of the unsubstantiated dossier alleging a conspiracy between President Trump and Russia," the letter said.



"It is highly troubling that Fusion GPS appears to have been working with someone with ties to Russian intelligence -- let alone someone alleged to have conducted political disinformation campaigns -- as part of a pro-Russia lobbying effort while also simultaneously overseeing the creation of the Trump/Russia dossier. The relationship casts further doubt on an already highly dubious dossier," it said.



In a closely related matter, U.S. federal prosecutors have been engaged in a multiyear battle in U.S. courts to seize what they say are some of the proceeds netted from the original $230 million tax fraud in Russia.



Тhat case, known as USA v. Prevezon, alleges that a Russian businessman named Denis Katsyv used some of the Magnitsky funds, after they were laundered through European banks, to buy real estate in Manhattan.



Тhe case, which has prosecutors seeking to seize more than $11 million in real estate and bank accounts, went on hiatus last year after a U.S. judge threw the defendants' lawyer, Baker Hostetler, off the case.



Last month, the defendants’ new lawyers again asked the U.S. judge to throw out the case.