More than 40 former U.S. attorneys and Republican and conservative officials are pushing back against efforts to discredit the special counsel investigating Russian interference in the 2016 election.

In a pair of letters, the groups say Robert Mueller and his team must be allowed to continue their work, unimpeded.

The 22 former U.S. attorneys, who served under presidents from Richard Nixon through Barack Obama, say it is "critical" to the "interests of justice and public trust to ensure that those charged with conducting complex investigations are allowed to do their jobs free from interference or fear of reprisal."

Seeking Mueller's removal "would have severe repercussions for Americans' sense of justice here at home and for our reputation for fairness around the world," they wrote in a letter to President Donald Trump on Friday that was coordinated by Georgetown Law's Institute for Constitutional Advocacy and Protection.

Another letter signed by 22 Republican and conservative former members of Congress and other top U.S. officials says efforts to discredit Mueller's work "undermine the institutions that protect the rule of law and so our nation."

"We urge the Administration, members of Congress on both sides of the aisle, and the American public, to support the work of Special Counsel Mueller to its conclusion, whatever it may be," reads the open letter signed by officials including former Defense Secretary Chuck Hagel, former State Department counselor Eliot Cohen and former George W. Bush administration ethics lawyer Richard Painter.

The letters come as Mueller's team is facing heightened scrutiny in recent weeks following reports that two FBI officials who would later be assigned to the special counsel's investigation called Trump an "idiot" and "loathsome human" in a series of text messages last year.

Peter Strzok, a veteran FBI counterintelligence agent, was removed from Mueller's team over the summer following the discovery of text messages exchanged with Lisa Page, an FBI lawyer who was also detailed this year to the group of agents and prosecutors investigating potential coordination between Russia and Trump's Republican campaign.

Allies of the president have seized on the messages and other details about Mueller's team to allege it is biased against Trump.

Trump has repeatedly called investigations into his campaign a "witch hunt" fueled by Democrats still angry about his election win.

Still, Trump and White House officials have said recently that he has no intention of firing Mueller. That decision that would likely be up to Deputy Attorney General Rod Rosenstein, who appointed the special counsel.

Mueller's investigation has so far netted charges against four people, including former national security adviser Michael Flynn, who has pleaded guilty to lying to the FBI.