Two powerful Republican senators are denouncing the FBI for saying its long-running investigation of Hunter Biden was fueled by “Russian disinformation.” This comes as multiple House committees accelerate their probes into the first son’s finances as well as into the Department of Justice’s handling of his case.

Senators Grassley and Johnson now say their investigation of the younger Mr. Biden, which began in 2019 when the GOP held a Senate majority, has been hamstrung at every turn by a “politicized” FBI. 

 The two men — Mr. Grassley, who was then the chairman of the Finance Committee, and Mr. Johnson, who was then the chairman of the Homeland Security and Governmental Affairs Committee — combed through records dating back more than a decade to dig into the origins of Mr. Biden’s foreign business dealings, which have been criticized for self-dealing and using the Biden name to make money from shady overseas actors. 

The senators’ report, released in September 2020, showed that not only the younger Mr. Biden but many of his family members had benefited from the lucrative deals he made overseas in countries like Kazakhstan, Russia, and Communist China, among others. 

In an interview with Fox News Digital on Thursday, the two senators sharply criticized the FBI for claiming to them that evidence of Mr. Biden’s alleged corruption was Russian “disinformation.”

In August 2020, one month before Messrs. Grassley and Johnson released a report detailing Mr. Biden’s financial transactions and ties to foreign governments, the FBI held a briefing for members of the Senate in which agents claimed that negative  information related to the Biden family was being disseminated by the Russian government and its allies to sway the outcome of the 2020 presidential election. 

In a letter sent in August 2022, two years after the original briefing, Mr. Grassley told FBI officials that the meeting was “unnecessary” and only occurred “because of pressure from our Democratic colleagues.” Details of that meeting, Mr. Grassley noted, were later leaked to the press. 

“The more we learn about what the FBI was up to in the summer of 2020, the more questions we have about what was done with information related to the Hunter Biden investigation,” Mr. Grassley said in his Thursday interview with Fox. He said he now realizes that the FBI’s briefing was a “clear effort to discredit our oversight.”

Mr. Johnson asserted in the same interview that the FBI has been injecting itself into other congressional investigations of the first son in order to protect the president. “As troubling as Biden family corruption is — and the extent to which it compromises American foreign policy — there is a much larger story of corruption to be uncovered,” he said. “The complicity of federal law enforcement and the unequal application of justice is a true threat to our democracy.”

Messrs. Grassley and Johnson also accused the FBI of stonewalling the FBI’s own employees, preventing them from investigating corruption allegations against the younger Mr. Biden. The FBI “instructed employees not to look at the Hunter Biden laptop immediately after the FBI had obtained it,” the two senators alleged. 

In their 2020 report, released just weeks before the New York Post gained access to the first son’s now infamous laptop, Messrs. Grassley and Johnson detailed the extensive ties the future first son had with foreign businesspeople. The primary focus of the report was Mr. Biden’s employment as a board member of the Ukrainian energy company Burisma, which was paying him as much as $80,000 a month, and how his work for the company coincided with the overthrow of the country’s president and deep civil unrest. His father, at the time, had been a designated Obama administration point person on Ukraine.

Mr. Biden’s financial records “show potential criminal activity relating to transactions among and between Hunter Biden, his family and his associates with Ukrainian, Russian, Kazakh and Chinese nationals,” the report stated. The senators also cited a number of American diplomatic officials who contemporaneously raised concerns about Mr. Biden’s employment with Burisma, but were rebuffed by the Obama administration. 

These accusations come as FBI and Department of Justice officials prepare for high-profile testimony before hostile congressional committees in the coming months. In July, the FBI director, Christopher Wray, will sit before the House Judiciary Committee, and Attorney General Garland will follow suit in September. 

The Judiciary Committee, led by Congressman Jim Jordan, has styled itself as the investigator of the investigators. Mr. Jordan’s summer plans include probing whether DOJ officials improperly injected themselves into the United States attorney for Delaware’s investigation into the younger Mr. Biden. 

Mr. Jordan has also said he hopes to speak soon with that U.S. attorney, David Weiss, about whistleblower allegations that he was not permitted by justice department higher-ups to bring felony charges against the first son. 

The House Ways and Means Committee recently involved itself in the same subject area after the panel’s chairman, Congressman Jason Smith, disclosed hours of testimony from two Internal Revenue Service whistleblowers who claim to have proof that Mr. Weiss’s investigation was halted at several points by DOJ superiors when he sought to bring charges in districts other than that of Delaware. 

Mr. Smith also unearthed transcripts of text messages from 2017 between Mr. Biden and a business partner from Communist China in which Mr. Biden invoked his father’s name, claimed the then-former vice president was by his side, and said he would “forever hold a grudge” if he did not receive payment. 

The House Oversight Committee, for its part, has been investigating what it calls a vast network of shell companies used to move money from foreign entities to members of the Biden family. The committee chairman, Congressman James Comer, disclosed that Biden family members had received $10 million through Mr. Biden and his associates over the course of years. He also recently subpoenaed a former business partner of the first son, Devon Archer, who is speaking with the committee about testimony. 

Mr. Comer claimed this week on a podcast appearance that the Biden family engaged in “organized crime” following his alleged discovery of “six policy decisions” that Vice President Biden made in exchange for a bribe from a Ukrainian business magnate.