A Pentagon investigation ordered by Defense Secretary Pete Hegseth has come under fire amid accusations that a warrantless wiretap was used on a former aide as part of the probe to find the source of internal leaks, The Guardian reported Tuesday.

White House officials, including Vice President JD Vance, were told that three aides fired by Hegseth, including former senior adviser Dan Caldwell, were outed by the illegal National Security Agency wiretap, according to the report. 

As a result, the White House has lost confidence in the integrity of the Pentagon's probe, The Guardian reported. Further, White House advisers have no idea who or what to believe, the report said.

If true, the use of an illegal wiretap would prove more of a scandal than the leaks themselves, according to the report.

"President Trump is confident in the secretary's ability to ensure top leadership at the Department of Defense shares their focus on restoring a military that is focused on readiness, lethality, and excellence," a White House spokesperson told The Guardian in a statement.

Caldwell, along with Hegseth's former deputy chief of staff, Darin Selnick, and the deputy Defense secretary's chief of staff Colin Carroll were fired last month after a top secret document regarding options for the U.S. military's role in reclaiming the Panama Canal was leaked to a reporter. The leak was attributed to Caldwell.

Hegseth's personal lawyer Tim Parlatore was tasked with the investigation, according to the report. 

The White House was told Caldwell printed out the top secret document, took a photo of it, and sent it to a reporter using his personal phone, according to the report. At the time, the Pentagon said Caldwell was dismissed for unauthorized disclosure of department information.

Caldwell publicly decried his dismissal and went on Tucker Carlson's podcast weeks later to say his firing, as well as those of Selnick and Carroll, were related to office politics. Parlatore was close to Hegseth's former chief of staff Joe Kasper, who left his post voluntarily in April amid the leak turmoil, according to the report.

White House officials pressed Parlatore as to how the Pentagon knew what was on Caldwell's phone, leading Parlatore to suggest that a warrantless wiretap was used, according to the report.

The warrantless wiretap has not been formally resolved, according to the report.

The investigation was transferred to Deputy Defense Secretary Stephen Feinberg's office around the same time that Parlatore needed to step away from the probe on other business, according to the report.

• WH Balks on Hegseth Top Aide Amid Criticisms
• Hegseth’s Chief of Staff Kasper to Leave Post Within Days