Washington (CNN) -- Sen. Charles Grassley on Friday stepped up his dispute with the White House over Operation Fast and Furious, as three of his Judiciary Committee investigators were provided to bolster Grassley's claim that President Barack Obama's spokesman was wrong Thursday about the fight over documents.
Grassley, R-Iowa, on Thursday said White House Press Secretary Jay Carney was inaccurate in his contention that the Justice Department had responded to requests for all documents on the botched gun-running operation.
"His statement that the administration has 'provided Congress every document that pertains to the operation itself' is hogwash," Grassley declared in a memo to reporters. "Through my investigation I know there are reams of documents related to 'the operation itself' that the Justice Department has refused to turn over to Congress," Grassley said.
Friday, the three Republican investigators for Grassley from the Senate Judiciary Committee provided reporters with a two-page list of internal reports, e-mails and investigative summaries which they said Attorney General Eric Holder had not turned over.
The investigators declined to say how they knew specifically what had not been provided, but it is widely believed that whistleblowers are a major source of the information.
Grassley is the ranking Republican on the committee.
Grassley, a critic of the Justice Department and FBI under both the Bush and Obama administrations, rejects the Obama White House assertion that Grassley is motivated by partisan politics.
"The accusation that I'm motivated by a desire for a 'political scalp' is baseless," Grassley said in his written statement.
The investigators Friday briefed reporters on Capitol Hill over the tug-of-war on documents pertaining to the illegal "gun walking" of firearms into Mexico to drug cartels and criminal gangs.
The Bureau of Alcohol, Tobacco, Firearms and Explosives launched Operation Fast and Furious out of Arizona to track weapon purchases by Mexican drug cartels.
However, it lost track of more than 1,000 firearms that the agency had allowed straw buyers to carry across the border, and two of the lost weapons turned up at the scene of the 2010 killing of U.S. Border Patrol agent Brian Terry. Ballistics test have not linked them to his killing.
The program has since been discontinued.