The US military routinely manipulated intelligence to play down the growing threat of ISIS — with 40 percent of analysts saying they had experienced attempts to distort their findings, a new congressional report alleges.

The report — a joint effort from the chairmen of the House Armed Services Committee, the House Permanent Select Committee on Intelligence and the House Appropriations Subcommittee on Defense — offers the findings of an investigation into efforts by the military’s Central Command (CENTCOM) to paint a rosy picture of the war on ISIS.

The report revealed that senior leaders produced reports that “were consistently more optimistic regarding the conduct of US military action than that of the senior analysts.”

A leadership change at CENTCOM in 2014 led to a “deteriorated” environment, where analysts said their work was distorted.

“Survey results provided to the Joint Task Force demonstrated that dozens of analysts viewed the subsequent leadership environment as toxic, with 40% of analysts responding that they had experienced an attempt to distort or suppress intelligence in the past year,” the report said.

The findings — produced by Republicans — come in response to a whistleblower complaint from May 2015.

But CENTCOM did not make improvements even after the whistleblower came forward.

“The Joint Task Force is troubled that despite receiving the whistleblower complaint in May 2015 and receiving alarming survey results in December 2015, neither CENTCOM, the Defense Intelligence Agency (DIA), the Under Secretary of Defense for Intelligence, nor the Office of the Director of National Intelligence (ODNI) took any demonstrable steps to improve the analytic climate within CENTCOM,” the report states.

“After months of investigation, this much is very clear: from the middle of 2014 to the middle of 2015, the United States Central Command’s most senior intelligence leaders manipulated the command’s intelligence products to downplay the threat from ISIS in Iraq. The result: consumers of those intelligence products were provided a consistently ‘rosy’ view of U.S. operational success against ISIS. That may well have resulted in putting American troops at risk as policymakers relied on this intelligence when formulating policy and allocating resources for the fight,” Rep. Mike Pompeo (R-Kan.), a member of the House Permanent Select Committee on Intelligence, said in a statement.

Rep. Bard Wenstrup (R-Ohio) added, “[O]ur investigation has determined that unfavorable intelligence reports underwent significant scrutiny and were likely to be omitted unless they could be confirmed with virtually 100 percent certainty. As a Lieutenant Colonel in the Army Reserve, I understand that intelligence is not always certain. Possibilities and probabilities can be just as critical for decision makers. Additionally, despite nearly nine months of review, we still do not fully understand the reasons and motivations behind this practice and how often the excluded analyses were proven ultimately to be correct. We cannot win the war against ISIS with incomplete intelligence.”