Leaders of the United States Central Command (CENTCOM) manipulated intelligence to make efforts against the Islamic State (ISIS) in Syria and Iraq look more successful than they were in reality, according to a new report by a House Republican joint task force created to investigate the matter.

The group's findings corroborate reports that the environment at CENTCOM was "toxic," as senior officials there pressured analysts and whitewashed intelligence reports.

Starting in mid-2014, CENTCOM disseminated intelligence that was "more optimistic than actual events warranted" and "consistently more optimistic" than that of other intelligence agencies and its own senior analysts, the group's review said.

As the fight against ISIS intensified, senior leadership "increased their involvement in the review and editing of … intelligence assessments."

"While senior leaders denied that operational reporting was biased in a particular direction, multiple analysts disagreed, noting that the deference to operational reporting resulted in analysis that was more positive regarding the capabilities of the [Iraq Security Forces] and the progress of the fight against [ISIS] than could be justified or supported by the vetted, serialized intelligence reporting on which analysts customarily rely," the report said.

Pressure to whitewash intel at CENTCOM was pervasive, with two in five analysts telling the task force that they had "experienced an attempt to distort or suppress intelligence in the past year." Other analysts refused to testify, the task force said, possibly "out of fear of potential reprisals."

Kansas representative Mike Pompeo, a member of the task force, said that CENTCOM's botched intelligence contaminated the public sphere and endangered America's national security.

"Claims that ISIS was the 'JV team' and that al-Qaeda was 'on the run' were both a result—and a cause—of the politicization of intelligence at CENTCOM," Pompeo said in a statement. "This intelligence manipulation provided space for both ISIS and al-Qaeda to grow and it put America at risk."

In public remarks and congressional testimony, defense officials distorted the fight against ISIS, claiming that the Islamic State was on the defensive or "losing ground" only to be debunked by reality when ISIS maintained or overtook territory, the report said.

Such comments mirrored claims from Obama and Secretary of State John Kerry that the U.S. was defeating ISIS.

CENTCOM officials often teleconferenced with intelligence officials, including Director of National Intelligence James Clapper, ahead of his daily intelligence briefings to Obama, the task force said.

The House investigation was sparked by a whistleblower's allegations that senior leaders at CENTCOM were manipulating intelligence reports. The task force was also led by California representative Ken Calvert and Ohio representative Brad Wenstrup, and was established by the House Armed Services Committee, the House Permanent Select Committee on Intelligence, and the House Appropriations Committee.