Republican U.S. Rep. Elise Stefanik called for U.S. Defense Secretary Lloyd Austin to resign after his secretive hospital stay and delay in informing the Biden administration.

The New York congresswoman, who is also the chair of the House GOP Conference, also called for an investigation into the matter.

The Pentagon said Sunday Austin had a medical procedure Dec. 22, went home a day later and was admitted to intensive care Jan. 1 when he began experiencing severe pain. The Pentagon failured to disclose Austin's hospitalization, including to President Joe Biden, the National Security Council and top Pentagon leaders. Biden was told of Austin's medical stay on Thursday, the Associated Press reported.

"In the chain of command, the Secretary of Defense serves as the connection through which the President commands and controls our armed forces. At this dangerous time when American service members are under attack in Iraq and Syria, our closest partner and ally Israel is at war with Hamas terrorists, and the threat from Communist China is on the rise, it is critical that the Secretary of Defense has the full trust of the American people, Congress, and the White House," Stefanik said in a statement Monday. "This concerning lack of transparency exemplifies a shocking lack of judgment and a significant national security threat. There must be full accountability beginning with the immediate resignation of Secretary Austin and those that lied for him and a Congressional investigation into this dangerous dereliction of duty.”

Austin, 70, remains hospitalized and officials have been unable to say how long he will be at Walter Reed.

Austin was a commanding general at Fort Drum from September 2003 to August 2005.

Fort Drum is also in Stefanik's congressional district.

The Associated Press contributed to this report.