Updated

ISIS intelligence assessments have been modified to use measures such as the number of sorties and body counts, something that has not been widely used since Vietnam, to paint a more positive picture of the progress made by the U.S. government strategy, according to sources familiar with allegations made by analysts at Central Command (CENTCOM.)

Critics say this "activity based approach" to battle damage assessments does not present a comprehensive picture of whether ISIS is being degraded, nor does it reflect its resiliency.

For example, despite the year-long campaign to target oil refineries, the terror group has built temporary facilities and maintained the ability to raise money.

Two sources, including Rep. Mike Pompeo, R-Kan., said the investigation to date shows it is not a problem that begins and ends with CENTCOM, but rather the evidence indicates pressure from Washington.

"What we have seen so far raises real questions, not only about politicized intelligence at the level of the central command, but pressure that they may well have received from the top," Pompeo, who sits on the House Intelligence Committee, told Fox News.

While the ongoing investigation limited his comments, Pompeo added, "...from senior officials, political officials, not direct, but enough that it would taint the analysis."

In addition to modifying the metrics, a source familiar with the allegations by the analysts said executive summaries for the intelligence reports were "glossed up" to be more positive, though the underlying data was not changed, on the belief most policy makers would review the summary only. A third allegation is that the analysts nominated targets, "command and control" centers for ISIS in Syria, but they were denied.

Fox News was told at least two emails were sent by a senior manager to a small group of core analysts implying they should "tow the line," adding the emails were provided to the Inspector General, the independent Defense Department watchdog who is investigating the case, though a spokeswoman has not commented on specific evidence.

The IG spokesman said in a statement: "The investigation will address whether there was any falsification, distortion, delay, suppression, or improper modification of intelligence information; any deviations from appropriate process, procedures, or internal controls regarding the intelligence analysis; and personal accountability for any misconduct or failure to follow established processes."

National Intelligence Director James Clapper has been singled out for his twice weekly contact with the intelligence chief at CENTCOM, and his counterpart who works for the Joint Chiefs of Staff, as well as a civilian deputy, Gregory Ryckman.  Clapper denied he had any role politicizing the intelligence, in a September email, first reported by Fox News.

“…whatever flaws I have, politicizing intelligence isn't one of them,"  Clapper wrote.