Top Democrats in the Senate are seeking to confirm Trump administration official Sebastian Gorka is under investigation for not disclosing he was a member of a Hungarian neo-Nazi organization in his U.S. naturalization application.

"As a senior counterterrorism adviser, Mr. Gorka is in a position of great importance and public trust," U.S. Senators Dick Durbin, D-Ill., Richard Blumenthal, D-Conn., and Ben Cardin, D-Md., wrote in a letter to the Departments of Homeland Security and Justice released Monday. "The American people are entitled to know if a senior White House official is under criminal investigation."

Leaders of Vit├ęzi Rend, a group the State Department considers to have once been under the direction of Nazi Germany, have identified Gorka as a member who took a "lifelong oath of loyalty," according to reports cited by the senators.

Durbin, Blumenthal and Cardin originally called for an investigation of Gorka in March.

The trio acknowledged the departments often do not comment on investigations, but do sometimes confirm they are ongoing.

"We are also concerned that, according to numerous media reports, Mr. Gorka has been unable to obtain a security clearance, which could be a result of an ongoing criminal investigation," they wrote. "It is unclear how Mr. Gorka can effectively advise the president on counterterrorism and other national security matters without a security clearance."