A secretive Pentagon UFO data retrieval program has been hidden from Congressional oversight since 2017, a new report claims.

Whistleblowers assert the program — codenamed 'Immaculate Constellation' — was established to 'detect' and 'quarantine' the military's best UFO imagery, as well as its best videos, eyewitness testimonies and electronic sensor evidence.

This trove of high quality, multi-sensor UFO data is so tightly held that 'talking about it will put you in the danger zone,' according to a US official who confirmed the leak.

The quite literally 'above top secret' program allegedly sprang into action in the wake of the 2017 leak of three, still-as-yet unexplained US Navy infrared UFO videos.

A Pentagon spokesperson denied the existence of the program Tuesday evening, telling reporters: 'The Department of Defense has no record, present or historical, of any type of SAP [Special Access Program] called 'IMMACULATE CONSTELLATION.''

By law, classified programs like SAPs must be disclosed to the so-called 'Gang of Eight,' which includes the chairs and ranking members of the House and Senate Intelligence Committees and other key lawmakers. 

However, the source of the leaked report, who supplied the document to the independent news site Public, described the program as an 'Unacknowledged Special Access Program' or USAP with unique secrecy privileges.

Reporting in defense publication Jane's Defense first revealed the existence of USAPs decades ago, showing that government officials were authorized to lie publicly to deny their existence. 

Public's anonymous source alleged that such deceptions were now occurring on the issues of non-human intelligence (NHI) and unidentified aerial phenomena (UAP).

'The Executive Branch has been managing UAP/NHI issues without Congressional knowledge, oversight, or authorization for some time, quite possibly decades,' this anonymous whistleblower wrote in their report to Congress.