Harris sent a letter to Steve Linick, the State Department's inspector general, asking him to probe if any department officials worked with Giuliani "in violation of restrictions on engaging in partisan political activities" after Giuliani was referenced in a whistleblower complaint against Trump.

ADVERTISEMENT "I am particularly concerned that Department officials might have been aware of or aided Mr. Giuliani in violation of law or regulations against engaging in partisan political activities," Harris wrote in the letter released Thursday.

Harris, who is running for president, wants an initial response from the inspector general by Oct. 3.

Giuliani has come under growing scrutiny following reports that he and Trump urged Ukrainian officials to investigate Biden and the Democratic presidential front-runner's son, Hunter Biden.

Trump asked Ukrainian President Volodymyr Zelensky in a July 25 phone call to work with Giuliani and expressed hope that he would “look into” Biden's role in the firing of a Ukrainian prosecutor, according to a reconstituted transcript of the call released by the White House on Wednesday.

A separate whistleblower complaint released Thursday alleges that two State Department officials spoke to Giuliani "in an attempt to 'contain the damage' to U.S. national security" over his communication with Ukraine.

Giuliani denied the charges against him during an interview with CNN, including the whistleblower's account that multiple U.S. officials were “deeply concerned” about his communication with Ukrainian officials.