Deputy Attorney General Rod Rosenstein told a congressional hearing on Wednesday that he does not see good cause to fire special counsel Robert Mueller.
Rep. Jerrold Nadler, D-N.Y., asked Rosenstein whether he had seen any reason to fire Mueller, who is leading the investigation of the Trump campaign's alleged ties to Russia.
"No," Rosenstein responded at the hearing before the House Judiciary Committee.
"If there were no good cause, I would not" fire Mueller, a former FBI director, Rosenstein added, even if he were asked to do so. "I believe he was an ideal choice for this task," he said later.
Rosenstein's comments come after a week in which the Russia probe faced escalating criticism from conservatives.
House Republicans grilled the Department of Justice official about alleged improprieties in the conduct of the special counsel's investigatory process.
"Reports on the political predisposition, and potential bias, of certain career agents and department lawyers on special counsel Mueller's team are deeply troubling to all citizens who expect a system of blind and equal justice," House Judiciary Chairman Bob Goodlatte, R-Va., said in his opening statement.
"The Mueller team overwhelmingly ought to be attired with Democratic donkeys," said Rep. Steve Chabot, R-Ohio.
Mueller's probe has been hit by allegations of impropriety after texts between former Mueller investigators Peter Strzok and Lisa Page were made public. The texts showed that the two traded barbs about President Donald Trump during the campaign, and support for Hillary Clinton.
Trump attorney Jay Sekulow called Tuesday for a second special counsel to look into what he said were conflicts of interest at the Department of Justice and the FBI. Sekulow told CNBC that his call for a second special counsel had "nothing to do" with Mueller.
The alleged conflicts of interest Sekulow cited include a senior Justice Department official, Bruce Ohr, meeting with a former British spy during the 2016 election. Ohr's wife reportedly worked for a firm that was conducting opposition research on Trump.
Ohr was demoted from his position of associate deputy attorney general.
Sol Wisenberg, a white-collar attorney who served as deputy independent counsel during the Whitewater investigation, called Ohr's meeting "extremely unusual behavior." But, he said, the appointment of a special counsel would not be appropriate in this circumstance because there is no underlying criminal investigation.
Rosenstein said Tuesday he would not be permitted to appoint a special counsel to look into the conflict of interest allegations in the absence of a criminal investigation.
Rosenstein, who has overseen the probe after Attorney General Jeff Sessions recused himself, said Thursday that he was "satisfied" with the progress of the investigation.