Top Democrats from the House and Senate are demanding to know whether the Justice Department’s ethics chief advised acting attorney general Matthew G. Whitaker to recuse himself from special counsel Robert S. Mueller III’s probe of the Trump campaign’s Russia ties, citing “serious ethical considerations” that they say should keep him from overseeing the investigation.

In their letter, seven leading Democrats ask ethics chief Lee Lofthus to tell them “immediately” whether he or others advised Whitaker to recuse himself from overseeing the Mueller probe or provided other ethical guidance related to his new job leading the Justice Department. The letter argues that Whitaker’s stated views about Mueller and past connections to the Trump campaign “indicate a clear bias against the investigation that would cause a reasonable person to question his impartiality.”

Senate Minority Leader Charles E. Schumer (D-N.Y.); House Minority Leader Nancy Pelosi (D-Calif.); the top House and Senate Judiciary Committee Democrats, Sen. Dianne Feinstein (D-Calif.) and Rep. Jerrold Nadler (D-N.Y.); the top Intelligence Committee Democrats in both chambers, Sen. Mark R. Warner (D-Va.) and Rep. Adam B. Schiff (D-Calif.); and the ranking Democrat on the House Oversight Committee, Rep. Elijah E. Cummings (D-Md.), have all been critical of Whitaker’s appointment to serve as acting attorney general since it was announced last week. In their letter to Lofthus, they repeated a number of the complaints about Whitaker that they have already aired, including his disparaging the evidence in the Mueller probe as “weak” and his concurrence with President Trump that the probe is “a mere witch hunt.”

They also pointed to Whitaker’s public statements that Mueller’s probe should be limited or defunded, as well as his affiliation with Sam Clovis, who was the Trump campaign’s national co-chairman, as evidence that he is too biased against Mueller’s investigation to oversee it.

“The official supervising the Special Counsel investigation must be — in both fact and appearance — independent and impartial,” they wrote. “Allowing a vocal opponent of the investigation to oversee it will severely undermine public confidence in the Justice Department’s work on this critically important matter.”

Whitaker has not indicated that he has any plans to recuse himself from overseeing the Mueller probe. A spokeswoman for the Justice Department did not immediately respond to a request for comment on the Democrats’ letter.

House Democrats have pledged to investigate Whitaker’s actions as acting attorney general, particularly pertaining to the Mueller probe, as soon as they assume the House majority in January.

Nadler said on CNN’s “State of the Union” on Sunday that Whitaker would be the first witness he calls before the House Judiciary committee.

And Schiff has pledged to investigate not just Whitaker but any issues he may try to prevent Mueller from addressing in the course of his probe.

“The House can both do its own investigation of the underlying issues and also investigate whether the president obstructed justice through the appointment and actions of Whitaker, or if the acting AG acted inappropriately on his own,” Schiff said in an interview late last week. Democrats, he added, would “need to deliver a message to the administration that we intend to scrutinize any action to interfere with the Mueller investigation.”

Acting attorney general Matthew G. Whitaker, center, and Labor Secretary Alex Acosta attend a wreath-laying ceremony Sunday at the Tomb of the Unknowns at Arlington National Cemetery. (Andrew Harnik/AP)