(CNN) The Democratic chairman heading the House Homeland Security Committee slammed Homeland Security Secretary Kirstjen Nielsen on Tuesday, saying she declined to appear at a hearing next month.
Committee chairman Rep. Bennie Thompson called Nielsen's decision "unreasonable and unacceptable," accusing her of using the shutdown as a cover and urging her to rethink the move in light of a possible second shutdown looming.
"Your attempt to use the President's recent shutdown as an excuse not to testify before Congress prior to the impending shutdown is outrageous," Thompson wrote Nielsen in a letter dated Tuesday. "As Secretary of Homeland Security, you should be prepared to testify on border security, the very issue that caused the recent shutdown, at any time and certainly prior to the potential February 15 lapse in appropriations."
"Your failure to engage Congress only makes averting another shutdown more difficult," he added.
A Department of Homeland Security spokesman called Thompson's letter misleading in a statement to CNN Tuesday.
"We are disappointed in Chairman Thompson's misleading letter," said DHS press secretary Tyler Q. Houlton. "To be clear, the Secretary did not 'refuse' the Chairman's invitation to testify. In fact, she accepted the invitation and proposed alternative dates in February, as the proposed date of February 6 was unworkable. This is a standard process in scheduling Congressional hearings. DHS separately updated the Chairman's staff that the Department would be delayed in responding to the Chairman's document requests because such functions were legally restricted during the shutdown."
"Unfortunately, instead of calling the Department or reaching out to the Secretary to identify a mutually workable alternative date, the Chairman chose to release a letter falsely claiming the Secretary was refusing to testify. Such missives are unproductive and unhelpful in sustaining comity between the Committee and the Department."
He added that the department hopes the committee will "choose constructive and professional engagement" in future communication.
In a statement provided to CNN on Wednesday, Adam Comis, the committee's communications director, said "there is nothing in the Chairman's letter that is false."
"The Secretary and her office were officially aware of our intentions to have her come testify before the Committee since January 4th," he wrote. "They indicated she would testify after the shutdown, which is now over. On January 23rd, two weeks before the proposed hearing, we officially invited her to come testify."
Comis said it was "unhelpful" for a DHS employee to wait nearly a week to notify the committee that the February 6 hearing date wouldn't work, adding that the department didn't give "any legitimate reason" for why it wouldn't.
Thompson's letter comes following two other congressional rejections from the Cabinet last week. Treasury Secretary Steve Mnuchin declined to testify before the Ways and Means Committee, and Health and Human Services Secretary Alex Azar declined to appear before the Energy and Commerce Committee. Ways and Means Chairman Richard Neal told CNN Tuesday that he and Mnuchin are looking at alternative dates.
Thompson stressed in the letter that he would follow through on his committee's oversight mandate, possibly hinting that the panel would compel Nielsen to appear.
"Please know that as chairman, I intend to ensure the committee fulfills its oversight responsibilities on this important matter," he wrote.
Thompson said last week, when he was still waiting for Nielsen's reply, that he was willing to subpoena her.
"I would hope she will accept the invitation," he told CNN Thursday. "There's a willingness to work with her on our part, but we won't hesitate if she chooses not to come to issue a subpoena."
CORRECTION: This story has been updated to accurately reflect Adam Comis's position as communications director for the House Committee on Homeland Security.