The alleged manipulation of intelligence to downplay the strength of terror groups is far more extensive than previously reported and goes back to at least 2012, according to the Republican chairman of the House intelligence committee.

The Defense Department inspector general and congressional investigators are reviewing claims that intelligence on the Islamic State was manipulated to present a more positive picture of the U.S. strategy's effectiveness. Rep. Devin Nunes, R-Calif., said these practices, though, extend to how intelligence on Al Qaeda was handled as well.

"I know for a fact this was going on in 2012, because I was told by informants that this was going on back then," Nunes, head of the intelligence committee, told Fox News. "We thought this was foolish, to pull all of our troops out of Iraq, because we thought, just from our own work, that this would be bad, but the administration was able to say, 'No, well, this is what the intelligence says.'"

While President Obama early last year, in an interview with The New Yorker, referred to ISIS as the "JV team," and has described Al Qaeda as "decimated," Nunes' suspicions were further confirmed by a 2013 incident at Florida's U.S. Central Command (CENTCOM).

Analysts at CENTCOM -- which oversees 20 nations, including Syria, Iraq and Pakistan -- were tasked with reviewing the documents recovered from Usama bin Laden's compound during the Navy SEALs raid. In May 2013, Nunes went to Florida for a briefing on the documents, but the intelligence analysts he expected to meet were not there.  Instead, the congressman was told the analysts were not working on a Saturday, which apparently was not true.

"We found out not only were they there, they were prepared to brief -- someone has to answer as to why they did not let us have access to those analysts," Nunes explained. The message that the analysts were not available was delivered by Maj. Gen. Scott D. Berrier, who headed the intelligence wing, but the congressman said the interference had to come from higher up.

A source close to some of the analysts indicated the manipulation of intelligence began on Berrier's watch. Berrier, who is now commanding general, U.S. Army Intelligence Center of Excellence & Fort Huachuca, told Fox News in an email, "I personally met with Representative Nunes on that Saturday as requested and we provided all available information." Citing an ongoing DoD investigation, he added that it would be inappropriate for him to comment further.

Nunes said in addition to the complaints that ISIS intelligence assessments hyped battlefield damage by the U.S. air campaign, and minimized the group's resilience, there were significant complaints about the handling of the Bin Laden documents. A military intelligence source close to the analysts, who was not authorized to speak on the record, said the CENTCOM atmosphere was one where a clear direction was implied, described as "daily rudder guidance."

Fox News is told the grievances were on a low boil until May when ISIS rolled through Ramadi with 30 car bombs, 10 the size of the 1995 Oklahoma City attack -- and the so-called happy talk about progress conflicted with the on-the-ground reporting.

The White House insisted Friday that no one in the administration pressured anyone, and suggested blame may rest with the military. "The inspector general, I believe it's a Department of Defense inspector general, that's considering actions that may or may not have been taken by a range of officials inside the Department of Defense. I don't think there are any accusations that have been made against the White House officials," White House Press Secretary Josh Earnest said.

Nunes said the House intelligence committee is now working with the House Armed Services Committee, led by Rep. Mac Thornberry, R-Texas, and House Oversight and Government Reform Committee, led by Rep. Jason Chaffetz, R-Utah, to present a "united front." Their investigation is encouraging more whistleblowers to come forward, with the guarantee of full congressional protections.