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WASHINGTON — The Department of Homeland Security's chief watchdog is calling for disciplinary action against a Trump administration political appointee who has refused to cooperate with an investigation into alleged retaliation against career civil servants, according to a memo released Thursday.

Christine Ciccone, a former senior official at the State Department and now an assistant secretary of legislative affairs at DHS, has failed to agree to an interview with investigators "despite repeated requests made to both her and her attorney over many months," DHS Acting Inspector General John Kelly wrote to Secretary Kirstjen Nielsen in a Feb. 13 memo.

The State Department Office of Inspector General (OIG) said a senior official's refusing to submit to an interview is "unprecedented."

That office is looking into allegations of retribution against career State Department employees, and has tried to speak with Ciccone as a "key witness" in that inquiry since September, Kelly wrote in a memo released by three Democratic lawmakers.

Multiple whistleblowers inside the department have contacted congressional committees alleging politically-motivated personnel decisions during Ciccone's time as deputy chief of staff to former Secretary of State Rex Tillerson, the lawmakers said in a statement.

State's OIG has "documentary evidence demonstrating Ms. Ciccone's involvement in personnel actions against at least three career employees," the office told congressional committees Monday.

But it could not finish the review as it had not been able to interview Ciccone, according to the lawmakers' statement.

Kelly recommended Secretary Nielsen discipline Ciccone due to her failure to cooperate.

U.S. Secretary of Homeland Security Kirstjen Nielsen speaks at the press briefing at the White House in Washington on June 18, 2018. Brendan Smialowski / AFP - Getty Images file

The appointee's response "sets a dangerous precedent contrary to the fundamental tenants" of the law establishing government inspector generals, and carries "the potential to undermine our critical oversight function," he wrote.

When asked about the memo, DHS did not say whether Nielsen would take any disciplinary action against Ciccone.

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The secretary "is reviewing the issue," DHS Press Secretary Tyler Houlton told NBC News in an email.

"Christine Ciccone is an exceptional member of the DHS team and has helped advance crucial efforts to secure our homeland during her time with the Department," Houlton said.

The State Department declined to comment on the record.

Through her lawyer, Ciccone has asked for access to her old email account at the State Department. The OIG has said she can have that access once she agrees to a date to meet its officials.

Ciccone rejected the OIG's portrayal of her response, telling NBC News in an email: "I have never refused to interview with the OIG."

"In order to cooperate, I proactively asked for materials from my tenure so I can be helpful in the OIG's process," she said, adding that she looked forward to addressing "the false implication that there was anything other than professional and appropriate management of personnel decisions."

The inspector general's office does not have legal authority to compel testimony through a subpoena, experts say.

Ciccone is just one of several officials who have come under scrutiny over allegations that career diplomats and civil servants have faced retribution from political appointees at the State Department since President Donald Trump entered office.

From center, Secretary of State Rex Tillerson, Senator Lisa Murkowski, R-AK, from left, and Tillerson's deputy chief of staff Christine Ciccone, from right, meet with US/Alaska Permanent Participants to the Arctic Council in Fairbanks, Alaska, on May 10, 2017. Nicholas Kamm / AFP - Getty Images file

Even though career civil servants take an oath to the Constitution and have a professional tradition of carrying out the policies of administrations from both sides of the political spectrum, whistleblowers have told lawmakers that political appointees in the Trump administration have allegedly questioned the loyalty of some career employees and sought to undercut them.

The memo on Ciccone was released by three congressional Democrats, House Foreign Affairs Chairman Eliot Engel, House Oversight Chairman Elijah Cummings and Senate Foreign Relations ranking member Bob Menendez. In a joint statement, the three lawmakers called Ciccone's behavior "outrageous."

The three lawmakers demanded Nielsen take prompt action to uphold the inspector general office's legal authority and to report back to their committees by Friday to update them on the case.

A Democratic congressional aide, who was not authorized to speak on the record, said the case was "another example of how Trump administration political appointees believe that the rules don't apply to them."

The State Department has said previously that Secretary of State Mike Pompeo would not tolerate political retribution against career employees.

But the congressional committees continue to hear complaints that political retribution allegedly persists in the department, two Democratic congressional staffers told NBC News.

In March 2018, Rep. Cummings and Rep. Engel obtained emails from a whistleblower that they say showed senior officials at the White House and the State Department worked with a network of conservative activists to try to remove or sideline career employees who were considered untrustworthy due to their work with the previous Obama administration or other reasons.

Among those allegedly targeted was a career civil servant, Sahar Nowrouzzadeh, who entered the federal government during President George W. Bush's administration. Nowrouzzadeh was singled out by a right-wing news outlet as insufficiently loyal to Trump and sympathetic to Iran. She wrote to her supervisor Brian Hook, then the director of the policy planning staff and now overseeing Iran policy at the State Department, asking for his help to "correct the record," according to the emails.

Hook forwarded her email to other political appointees at the State Department, who then passed it along to the White House. In the internal emails discussing her, officials cited her Iranian heritage and falsely claimed she was born in Iran.

Against her request and the scheduled term of her appointment to that office, Nowrouzzadeh's tenure on the policy planning staff was cut short by three months, according to the emails.