Democrats say a whistleblower central to a GOP-driven probe of a government decision that let Russia gain a foothold in the U.S. uranium market provided “no evidence” that former secretary of state Hillary Clinton was involved in the process, as President Trump alleged during the 2016 presidential campaign.

William Campbell, the confidential FBI informant who congressional Republicans believed could link a multiagency decision to approve the sale of uranium company shares to Russia with payments made to the Clinton Foundation, “was unable to point to anything to support his claims,” Democratic staffers wrote in a memorandum sent Thursday to members of the investigating committees. They also wrote that Justice Department officials told investigators Campbell “never provided any evidence or made allegations regarding Secretary Clinton or the Clinton Foundation,” and that “there were ‘no allegations of impropriety or illegality’ . . . in any of the documents they reviewed.”

The memo is the Democrats’ latest effort to stymie what they say are Republican attempts to distract from the various probes examining Russian interference in the 2016 U.S. elections, and alleged ties between Trump and Russian officials. Democratic congressional leaders questioned Campbell’s credibility in a letter sent last month to the chairmen of the House Intelligence and Oversight and Government Reform Committees. On Thursday, they raised more specific complaints with Campbell’s testimony in the memo sent to members of those panels and the Senate Judiciary Committee, all three of which are looking into issues surrounding the uranium deal.

The deal in question took place in 2010, when Russia’s atomic energy agency, Rosatom, acquired a controlling stake in Toronto-based company Uranium One, giving Russia rights to about 20 percent of the uranium extraction capacity in the United States.

Because the deal involved giving a foreign government control of an American business’ commodity, it had to be approved by the Committee on Foriegn Investment in the United States — a nine-agency board of which the State Department is a member, but not in a leading role. Clinton herself was never on the CFIUS board.

In one particularly pointed complaint, congressional Democrats said that Campbell “had no knowledge about” CFIUS or its processes, and had in his own words, “looked on Google to see what CFIUS was about” after the deal was concluded. He also told the committee that allegations that Russian influence via the Clintons affected the decision were “outside my pay grade” and “not my bailiwick.”

Democratic staffers wrote in the memo that they were compelled to draft and release it after Republicans declined several requests to release the transcript of the interview with Campbell.

A spokeswoman for Oversight and Government Reform Committee Chairman Trey Gowdy (R-S.C.) did not directly rebut the claims made in the memo.

“We appreciate Mr. Campbell’s service to our country and his willingness to appear before the Committee to answer questions related to our core investigative mission,” Gowdy spokeswoman Amada Gonzalez said in a statement Thursday, defining that mission as an effort “to determine what the FBI did or did not know at the time CFIUS approved the Uranium One deal, and how we can improve the CFIUS process and agency coordination moving forward.”