White House adviser Kellyanne Conway defied a subpoena to appear before the House Oversight Committee on Monday to face questions over alleged violations of the Hatch Act.

In a letter to House Oversight Chairman Elijah Cummings, D-Md., the White House said Conway is “absolutely immune” from having to testify before Congress due to her position in the White House.

"As you know, in accordance with longstanding, bipartisan precedent, Ms. Conway cannot be compelled to testify before Congress with respect to matters related to her service as a senior adviser to the president," wrote Pat Cipollone, counsel to the president. "The Department of Justice has advised me that Ms. Conway is absolutely immune from compelled congressional testimony with respect to matters related to her service as a senior adviser to the president."

SPECIAL COUNSEL RECOMMENDS FIRING KELLYANNE CONWAY OVER ALLEGED HATCH ACT VIOLATIONS

Speaking during Monday afternoon’s brief hearing, Cummings called the White House's claim “completely baseless."

“Our committee has heard testimony from many White House officials under both Republican and Democratic administrations," Cummings added. “We are requiring her to testify before Congress about her multiple violations of federal law, her waste of taxpayer funds and her actions that compromise public confidence in the integrity of the federal government.”

The House Oversight Committee voted 25-16 late last month to subpoena Conway to appear before it over a special counsel report finding that she'd violated the Hatch Act. Rep Justin Amash was the sole Republican to join the Democrats in what was otherwise a party-line vote. Amash has since left the Republican Party and declared himself an independent.

The Office of the Special Counsel, which is separate from the office with a similar name previously run by Robert Mueller, said in a scathing report in June that Conway violated the Hatch Act by “disparaging Democratic presidential candidates while speaking in her official capacity during television interviews and on social media," and recommended she be fired.

The Hatch Act's purpose is to ensure federal programs are “administered in a nonpartisan fashion, to protect federal employees from political coercion in the workplace, and to ensure that federal employees are advanced based on merit and not based on political affiliation,” according to the OSC.

The office is an independent federal agency that monitors compliance with that law and others.

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The ranking Republican on the oversight committee, Rep. Jim Jordan of Ohio, called the investigation into Conway the work of a “left-wing advocacy group” and criticized the committee for calling the hearing in the first place.

“This is another example of the committee using a hearing for politics,” he said.

Cummings said that if Conway does not reconsider appearing on Capitol Hill, the committee will hold a business meeting on July 25 to discuss holding her in contempt.

Fox News' Adam Shaw contributed to this report.