A federal watchdog said it will launch a review of the process by which the Justice Department and FBI obtained a surveillance warrant on a "certain U.S. person" amid allegations from Republican lawmakers that the FBI relied improperly on campaign opposition research to justify the warrant.

Michael Horowitz, the Justice Department’s Inspector General, is already probing allegations of political bias in several investigations leading up to the 2016 presidential election.

In a statement, the IG said it will determine what the Justice Department and FBI knew “at the time the applications were filed from or about an alleged FBI confidential source.”

“Additionally, the OIG will review the DOJ’s and FBI’s relationship and communications with the alleged source as they relate to the FISC applications. If circumstances warrant, the OIG will consider including other issues that may arise during the course of the review,” the IG said.

According to a statement, the review comes at the request from Attorney General Jeff Sessions, as well as numerous members of Congress.

Republican lawmakers — specifically those on the House Intelligence Committee — have claimed the federal government used information given to them by Christopher Steele, an ex-British spy, to obtain a warrant through the Foreign Intelligence Surveillance Court to wiretap Carter Page in 2016, a former adviser to President Trump's campaign.

Steele was hired by opposition research firm Fusion GPS, which was paid for in part by Clinton and the Democratic National Committee, and in attempting to get the surveillance warrant, the Justice Department and FBI did not tell the court.

This, Republicans say, is evidence of bias in the federal government’s probe into Russian meddling in the 2016 presidential election and possible ties to the Trump campaign.

Democrats have called the claim of wrongdoing unfounded, saying senior government officials is unfounded, and the political motivations behind Steele’s research was revealed to FISC.

Other lawmakers have also accused senior leadership in the Justice Department and FBI of being biased toward the Trump administration.

President Trump himself has claimed the FBI is biased against him. In February, he tweeted the court did not know of Steele’s Democratic ties.

"'The four page memo released Friday reports the disturbing fact about how the FBI and FISA appear to have been used to influence the 2016 election and its aftermath....,'" Trump wrote in a pair of tweets. "'The FBI failed to inform the FISA court that the Clinton campaign had funded the dossier....the FBI became.......a tool of anti-Trump political actors. This is unacceptable in a democracy and ought to alarm anyone who wants the FBI to be a nonpartisan enforcer of the law....The FBI wasn't straight with Congress, as it hid most of these facts from investigators.'"

The House Intelligence Committee recently ended its Russia probe; the Senate Intelligence and Judiciary committees’ probes are ongoing.

Special counsel Robert Mueller is also looking into Russia’s 2016 interference and possible ties to the Trump campaign.

In February, Sessions said the Justice Department’s IG would be probing alleged bias in obtaining surveillance warrants.

Horowitz’s office is also probing how the Justice Department and DOJ handled the Clinton email investigation ahead of the 2016 election, with results due out sometime this spring.

Earlier this month, the FBI’s No. 2 was fired by Sessions two days before his schedule retirement date.

McCabe's firing was in part because of what he told inspector general investigators regarding his communications with the media about the bureau’s handling of the Clinton email investigation.

“Andrew McCabe FIRED, a great day for the hard working men and women of the FBI - A great day for Democracy. Sanctimonious James Comey was his boss and made McCabe look like a choirboy. He knew all about the lies and corruption going on at the highest levels of the FBI!” Trump — who had often called McCabe biased — said in response to McCabe's firing.