Rep. Trey Gowdy and fellow Republicans on the House Select Committee on Benghazi said that former Secretary of State Hillary Clinton and the State Department acted in a “shameful” manner in failing to turn over emails from her private email server, making it “impossible” to know whether everything about the Sept. 11, 2012, attack in Libya that left four Americans dead will ever be known.

In the committee’s final report, being released Tuesday, Republicans assert that stonewalling by the Obama administration — especially the State Department, Pentagon and CIA — delayed the completion of the investigation for months. The committee even threatened to begin contempt of Congress proceedings against Secretary of State John Kerry and CIA Director John Brennan for failing to comply with its subpoenas, according to a section of the final report obtained by Politico ahead of its release.

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The report blasts the administration for what Republicans say was repeated and willful noncompliance with a congressional investigation, forcing the Benghazi panel to use a series of under-the-radar subpoenas, subpoena threats and a warning that the committee would initiate contempt-of-Congress proceedings against Kerry and other officials if the department did not accede to its demands for information. Republicans say the State Department still has failed to turn over several thousand pages of documents related to an Accountability Review Board investigation into Benghazi.

Overall, the select committee issued more than a dozen subpoenas to federal agencies, and threatened to issue dozens more, including to top White House aides, say committee sources and the report.

“This ‘who’s on first’ routine orchestrated by [Clinton’s] private counsel and the State Department, which is ostensibly an apolitical government entity, is shameful,” the report states. “It was not merely Congress and the people it represents who were misled and manipulated, the State Department and the Secretary’s email arrangement undoubtedly delayed access to what happened to four brave Americans in Benghazi and the government’s response before, during and after the attacks.”

And Democrats have accused the committee of conducting a two-year witch hunt, seeking information that was already known or impossible to produce and dragging out the investigation for maximum political damage. The State Department has been more measured in its response, but also pointedly denies accusations of foot-dragging in a statement Tuesday.

"The Department cooperated extensively with the Benghazi Committee," department spokesman Mark Toner said. "The Committee received documents, briefings, and/or witness interviews from us every single month between August 2014 and June 2016. The Department provided every single witness the Committee asked for—over 50 current and former employees appeared for interviews, often requiring them to travel from abroad. We made over 50 document productions, totaling over 100,000 pages of documents. We provided eight briefings to members (of Congress) and staff, and Department witnesses appeared at all four of the Committee’s hearings."

In her testimony to the Benghazi committee last year and in numerous public statements, Clinton has denied wrongdoing in regard to the email server.

Still, she has conceded that using private email at State, which she said she did for convenience, was a mistake. “Looking back, it would’ve been better if I’d simply used a second email account and carried a second phone,” she said in March 2015.

The long tussle between the committee and the Obama administration led to some dramatic moments, according to the report and committee sources. During one meeting with State Department officials to talk about their slow response to the committee’s demands, Phil Kiko, the Republican staff director, walked in and slapped a stack of 20 subpoenas on the desk. The committee was preparing to issue a wave of subpoenas to diplomatic security personnel who were on the ground in Libya before and during the attack. But after the threat, State Department officials complied with the committee’s requests and brought in two of the personnel each week for interviews.

Subpoena threats were also used to secure testimony from national security adviser Susan Rice and deputy national security adviser for strategic communications Ben Rhodes. The White House agreed to allow the aides to be interviewed but kept dragging out scheduling for those sessions despite multiple inquiries, committee sources said.

Kiko threatened a subpoena unless the White House agreed to the proposed deposition dates. White House counsel Neil Eggleston hopped on a plane a few days later with two other White House employees to see Gowdy in Charlotte, North Carolina. They then negotiated the terms of the Rice and Rhodes’ interviews, panel sources said.

The “Select Committee on the Events Surrounding the 2012 Terrorist Attack in Benghazi, Libya,” as the panel is formally known, received more than 75,000 pages of previously unreleased documents and interviewed dozens of new witnesses. However, the panel was still unable to obtain everything it wanted.

In probably the most closely followed section of the report — concerning Clinton’s use of a private email server that at one point was located in the basement of her home in Chappaqua, New York, and which is still under FBI investigation — Republicans condemned what they described as a “shell game” between Clinton’s lawyers and the State Department.

The committee knew by August 2014 that Clinton was using a private email address to conduct official State business. But Republicans were not aware of the “extent” that Clinton used that address or the fact that State Department officials did not have access to tens of thousands of Clinton emails and were trying to obtain them from her. State had been aware of the issue of Clinton emails for 14 months at that point, but it never told the committee.

When the Benghazi committee wrote David Kendall, Clinton’s lawyer, in early December 2014 seeking access to all of her emails, Clinton’s legal team privately sent them to the State Department instead. That made the department responsible for deciding what to turn over to the Benghazi panel, a process that took months to play out. Clinton and her lawyers had already gone through all the emails, deleting those she said were private and nonofficial, a move that infuriated Republicans.

“The manner in which the Secretary communicated during her tenure, the manner in which those records were housed and the manner in which the public record was self-scrutinized and self-selected makes it impossible to ever represent to those killed in Benghazi that the record is whole,” the report states.

The Clinton campaign and Democrats say that Republicans are just looking to score political points over the email issue, a claim supported by comments from House Majority Leader Kevin McCarthy (R-Calif.) and others last year. But the committee insists its “interest in the Secretary’s emails is limited to their relevance in the investigation of the Benghazi attacks.”

Gowdy and other Benghazi panel Republicans say Clinton is to blame for her own problems.

“Had she used state.gov or employed a method of preserving public records other than simply hiring a private legal counsel to store, vet and disclose those public records, this would have never become an issue for the Committee,” the report says.

In addition to their battles with Clinton and the State Department, Republicans say the CIA and Defense Department were also slow to turn over documents and schedule interview requests. That prompted the Benghazi panel in February to threaten to hold Brennan in contempt of Congress. The CIA eventually turned over a series of rarely shared interagent instant messages about what was happening during the attack — a type of document committee staffers say that has never been shared previously with Congress.

The panel also eventually scheduled interviews with lower-level CIA officials who told the committee that they had erred on intelligence reports they wrote on Benghazi, surprising investigators who had no idea the officials would admit to such a conclusion, committee staffers said.

Benghazi committee staffers were allowed to read CIA emails only at agency headquarters and were not allowed to take their notes from the review outside the building. These notes had to be kept locked at CIA headquarters. The CIA “eventually offered to allow Committee staff to take their notes back to Committee offices — but only if CIA staff first reviewed the notes and applied various redactions to them,” according to the report. The Benghazi panel complained that none of these restrictions were ever imposed on the House Intelligence Committee.

Benghazi panel Republicans complained about the Pentagon’s response as well.

“The Defense Department was initially cooperative but this cooperation diminished during the course of the Committee’s investigation culminating in a factually deficient letter from a political appointee deliberately mischaracterizing efforts to obtain access to witnesses,” the report states. This was in reference to an April letter from a Pentagon official, Stephen Hedger, that accused the panel of using “unproductive” and “unfair” tactics to obtain documents and witness interviews.

Toner, the spokesman at State, accused the committee of drowning government officials with unreasonable demands for documents that added little or nothing to the understanding of the Benghazi attacks.

"The Committee repeatedly refused to narrow or focus their requests. As a result, we reviewed hundreds of thousands of pages of irrelevant documents. Furthermore, a large amount of what we did provide the Committee is absent from the report," he said.

The Benghazi committee recommends that salaries for federal officials held in contempt of Congress be cut off and a special counsel be appointed for any criminal-contempt recommendation against an executive branch official. Right now, all such criminal cases are at the discretion of the Justice Department, which is highly unlikely to seek an indictment of an official from the same party as the president. In addition, the Benghazi panel wants an expedited process to handle civil contempt cases.