Rep. Adam Schiff Adam Bennett SchiffPelosi, Democrats unveil bills to rein in alleged White House abuses of power Chris Matthews ripped for complimenting Trump's 'true presidential behavior' on Ginsburg Trump casts doubt on Ginsburg statement, wonders if it was written by Schiff, Pelosi or Schumer MORE (D-Calif.), the likely next chairman of the House Intelligence Committee, said Sunday that Democrats will challenge the appointment of new acting Attorney General Matthew Whitaker.

"Yes and yes," Schiff told ABC's "This Week" when asked if Democrats would push back against Whitaker's appointment and if he is still concerned that he poses a threat to special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's investigation into Russia's election meddling and alleged collusion between President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE's 2016 campaign and Moscow.

"I think the appointment is unconstitutional," Schiff said, adding that Whitaker's appointment has to be subject to Senate confirmation.

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"But it's also in conflict with a more specific statute," he said. "There's a succession statute for the Justice Department, which makes it different from other departments."

Schiff said that succession statute cannot be preempted by presidential appointment.

"So it's a flawed appointment, but the biggest flaw from my point of view is that he was chosen for the purpose of interfering with the Mueller investigation," Schiff said, echoing claims of other Democrats.

Last year, Whitaker criticized the Mueller probe and explained how it could be undercut by strategies such as limiting its funding.

Reports indicate that Mueller is very close to filing his final report from his investigation.

Schiff warned on Sunday that Democrats will be keeping a very close eye on Whitaker.

"He needs to know that if he takes any action to curb what Mr. Mueller does, we’ll find out about it. We’ll expose it," Schiff said.