The criminal referral appears to make no assessment of the veracity of the dossier’s contents, much of which remains unsubstantiated nearly a year after it became public.
But the dossier has emerged as Exhibit A in Republicans’ insistence that Obama-era political bias could have affected the F.B.I.’s decision to open a counterintelligence investigation in July 2016 into whether Mr. Trump’s associates aided the Russia election interference.
Republicans, including the two senators, have argued that the dossier is tantamount to political opposition research, and claimed that it might have been used by the F.B.I. to open its investigation. They have also said it might have provided the basis for key investigative actions, including a secret court-approved wiretap of a Trump campaign aide.
Current and former American and foreign officials with direct knowledge of the investigation say that the federal inquiry did not start with the dossier, nor did it rely on it. Rather, they have said, the dossier and the F.B.I.’s discussions with Mr. Steele merely added material to what American law enforcement and spy agencies were gleaning from other sources.
Mr. Grassley’s decision to recommend criminal charges appeared likely to be based on reports of Mr. Steele’s meetings with the F.B.I., which were provided to the committee by the Justice Department in recent weeks.
It was not clear why, if a crime is apparent in the F.B.I. reports that were reviewed by the Judiciary Committee, the Justice Department had not moved to charge Mr. Steele already.
The circumstances under which Mr. Steele is alleged to have lied were unclear, as much of the referral was classified.
In a short cover letter dated Thursday but transmitted on Friday, the senators wrote, “Based on the information contained therein, we are respectfully referring Mr. Steele to you for investigation of potential violations of 18 U.S.C. § 1001, for statements the Committee has reason to believe Mr. Steele made regarding his distribution of information contained.”
That section of the federal criminal code refers to knowingly making false or misleading statements to federal authorities.
Mr. Steele had repeated contacts before and after the election with F.B.I. counterintelligence agents who were investigating links between the Trump campaign and Russians. The information he shared was apparently valuable enough that the F.B.I. at one point even considered bringing him on as a paid source. They only backed off the idea after the dossier became public in January 2017 and Mr. Steele’s identity became widely known, leading the bureau to conclude that he would no longer be able to function as a source for its investigation.
More recently, Mr. Steele has been in contact with the Justice Department’s special counsel, Robert S. Mueller III, who took over the investigation last year.
Anyone can make a criminal referral to the Justice Department, which is not obligated to take up the matter. But a recommendation from a senior senator who runs the committee that has oversight of the department comes with added weight.
The Justice Department had no immediate comment on the referral. But Fusion characterized the recommendation to charge Mr. Steele as a smear and an attempt to further muddy the inquiry into Russia’s interference.
“Publicizing a criminal referral based on classified information raises serious questions about whether this letter is nothing more than another attempt to discredit government sources, in the midst of an ongoing criminal investigation,” said Joshua A. Levy, the lawyer for Fusion. “We should all be skeptical in the extreme.”
Mr. Grassley is overseeing an array of inquiries related to the F.B.I. and its investigations of both Mrs. Clinton and the Trump campaign. He and Mr. Graham have repeatedly pressed the agency on its handling of the dossier in particular and fought to gain access to key agency witnesses and documents about the matter, reviewing a large tranche of such material in recent weeks.
Fusion GPS hired Mr. Steele, a former officer of Britain’s MI6 with deep connections in Russia, during the spring of 2016 to research Mr. Trump’s ties to Russia. His findings were ultimately compiled into 35 pages of memos outlining a multipronged conspiracy between the Russian government and the Trump campaign to boost his candidacy and hurt Mrs. Clinton, including corrupt business dealings and salacious details alleging an encounter between Mr. Trump and Russian prostitutes.
The firm was first hired by The Washington Free Beacon, a conservative website, in May 2016, and its work was later funded by the Democratic National Committee and the Clinton campaign.
This week has seen Mr. Grassley engage in a heated spat with Fusion over the testimony of one of its executives, Glenn R. Simpson. It began when Mr. Simpson and his partner, Peter Fritsch, published an op-ed article in The New York Times accusing Republicans of waging “a cynical campaign” to try to discredit the firm and its findings and calling on the relevant congressional committees to release transcripts of a series of closed-door interviews with the men.
A spokesman for Mr. Grassley, Taylor Foy, shot back, saying that Mr. Simpson had been less than transparent with the committee and had declined to provide public testimony or additional documents and answers requested after the interview. He also said and that “Mr. Simpson and his attorney demanded during the interview that the transcript be kept confidential.” A lawyer for Fusion GPS, Joshua Levy, in turn, disputed that account, and said that upon review, his client now wanted the transcript to be made public — a request Mr. Grassley has denied.
The senator is not the only prominent Republican lawmaker pressing the Justice Department and Fusion GPS for answers on the dossier. Representative Devin Nunes of California, the chairman of the House Intelligence Committee, has been locked in a standoff with the department over access to documents and witnesses he views as crucial to unraveling what the F.B.I. did with the dossier. And he has aggressively pursued Fusion GPS, subpoenaing the company’s bank records and sending two committee staff members to London last summer to try to meet with Mr. Steele unannounced.
A resolution with the Justice Department appeared to be imminent this week, after Rod J. Rosenstein, the deputy attorney general, and Christopher A. Wray, the F.B.I. director, paid an unexpected visit to Speaker Paul D. Ryan of Wisconsin. Mr. Nunes, whom Democrats have accused of acting to protect Mr. Trump, said in a statement after the meeting that he expected to gain the access he desired.