CNN  — 

The House Homeland Security Committee has issued a subpoena to acting Homeland Security Secretary Chad Wolf for a hearing next week as he faces whistleblower allegations that he urged department officials to alter intelligence.

“From the coronavirus pandemic to the rise of right-wing extremism to ongoing election interference, there are urgent threats requiring our attention,” Committee Chairman Bennie Thompson, a Mississippi Democrat, said in a statement Friday. “Mr. Wolf’s refusal to testify – thereby evading congressional oversight at this critical time – is especially troubling given the serious matters facing the Department and the Nation.”

In a Friday letter to Thompson, Assistant DHS Secretary Beth Spivey told the chairman, “The arguments in your letter are without merit,” adding in part that “the right of a President’s nominee to abstain from testifying on matters unrelated to his or her nomination while such a nomination is pending is an unwritten rule honored by Chairmen from both sides of the aisle for many decades.”

Wolf and DHS, Spivey said, “have been most cooperative” in supplying the committee “accurate and complete information” related to national security.

The witness list for next week’s hearing includes Wolf, FBI Director Christopher Wray and Christopher Miller of the National Counterterrorism Center.

The subpoena comes after CNN reported Wednesday that a whistleblower has alleged that top political appointees in DHS repeatedly instructed career officials to modify intelligence assessments to suit President Donald Trump’s agenda by downplaying Russia’s efforts to interfere in US elections and the threat posed by White supremacists.

The whistleblower, Brian Murphy, claims that Wolf instructed DHS officials earlier this year to “cease providing intelligence assessments on the threat of Russian interference” and, instead, focus their efforts on gathering information related to activities being carried out by China and Iran.

In a letter to Thompson on Tuesday, DHS stated that Wolf “is unable to accommodate your request to testify before the Committee on September 17.” The letter offered that Senior Official Performing the Duties of the Deputy Secretary Ken Cuccinelli “would be willing testify in the Acting Secretary’s stead.”

“Should the presence of SOPDDS Cuccinelli before the Committee in Acting Secretary Wolf’s stead not meet your needs, we can collaborate to find a later date for the Acting Secretary to make himself available to the Committee after his confirmation vote in the Senate,” the letter added. The White House sent Wolf’s nomination to serve as full Homeland Security secretary to the Senate on Thursday.

Thompson’s committee isn’t the only one pursuing testimony from department officials of late. Following the whistleblower report, House Intelligence Committee Chairman Adam Schiff will be expanding his committee’s investigation into the DHS Office of Intelligence and Analysis and will seek additional interviews with a slate of DHS officials.

Separately, the top Republican and Democrat on the Senate Intelligence Committee sent a letter to the same office stating it is investigating the claims made by Murphy.

This story has been updated to include Assistant DHS Secretary Beth Spivey’s letter to Thompson.

CNN’s Zachary Cohen contributed to this report.