Former House Speaker Newt Gingrich (R-Ga.) questioned early Monday special counsel Robert Mueller's ability to remain fair and impartial in his investigation into Russia's involvement in the 2016 presidential election.

"Republicans are delusional if they think the special counsel is going to be fair. Look who he is hiring.check [Federal Election Commission] reports. Time to rethink," Gingrich tweeted about Mueller, a former director of the FBI.

Republicans are delusional if they think the special counsel is going to be fair. Look who he is hiring.check fec reports. Time to rethink. — Newt Gingrich (@newtgingrich) June 12, 2017

Gingrich, an informal adviser to the president, also voiced his concerns about Mueller on Sunday. He accused former FBI Director James Comey of manipulating the Russia probe in order to effectuate the appointment of a special counsel, and he called on Congress to dismiss the special counsel altogether.

ADVERTISEMENT

"I think Congress should now intervene and they should abolish the independent counsel, because Comey makes so clear that it's the poison fruit of a deliberate manipulation by the FBI director leaking to The New York Times, deliberately set up this particular situation. It's very sick," Gingrich told radio host John Catsimatidis.

"It's very clear that Comey hates Trump," he added.

Gingrich effusively praised Mueller last month after his announcement as special counsel, calling him a “superb choice” with an “impeccable” reputation for honesty and integrity.

Robert Mueller is superb choice to be special counsel. His reputation is impeccable for honesty and integrity. Media should now calm down — Newt Gingrich (@newtgingrich) May 18, 2017

Comey acknowledged during his Thursday testimony before the Senate Intelligence Committee that he leaked a memo to the press that detailed his meeting with Trump, in which he allegedly asked Comey to "let go" of his investigation into former national security adviser Michael Flynn. Comey said he leaked the memo in the hopes that he would inspire the Justice Department to appoint a special counsel to independently look into the whether Russia interfered in the presidential election.

Deputy Attorney General Rod Rosenstein appointed Mueller, a former FBI director, as special counsel one day after The New York Times published an article detailing Comey's memo.

Marc Kasowitz, the president's personal attorney, said Comey should be investigated for leaking what he called "privileged" communications with Trump.

At least four members of Mueller’s special counsel team have donated to Democratic presidential campaigns and organizations.

Justice Department Deputy Solicitor General Michael Dreeben donated in 2008 to a political action committee for then-Democratic presidential candidate Barack Obama Barack Hussein ObamaObama warns of a 'decade of unfair, partisan gerrymandering' in call to look at down-ballot races Quinnipiac polls show Trump leading Biden in Texas, deadlocked race in Ohio Poll: Trump opens up 6-point lead over Biden in Iowa MORE as well as a PAC for Hillary Clinton Hillary Diane Rodham ClintonFox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio Trump, Biden court Black business owners in final election sprint The power of incumbency: How Trump is using the Oval Office to win reelection MORE in 2006.

Jeannie Rhee, who previously served as a deputy assistant attorney general and now works as a partner in the investigations practice at WilmerHale, donated to the Democratic National Committee as well as campaign PACs Obama in 2008 and 2011, and Clinton’s campaign in 2015 and 2016.

James Quarles, who worked as an assistant special prosecutor on the Watergate Special Prosecution Force and who also works as an attorney at WilmerHale, has a long record of donating to Democratic groups starting in 1987 for the PAC Dukakis for President. In 2016, he donated to Clinton’s PAC Hillary for America.

And Andrew Weissman, who oversees fraud cases at the Justice Department, donated six times to PACs for Obama’s presidential campaign as well as the DNC in 2006.

- Updated at 11:00 a.m.