Justice Department Inspector General Michael E. Horowitz told Senate and House lawmakers Thursday that the process of finalizing his report into potential Foreign Intelligence Surveillance Act (FISA) abuses ahead of the 2016 presidential election was "nearing completion," according to a letter obtained by Fox News.

The "lengthy" draft report "concerns sensitive national security and law enforcement matters," Horowitz wrote in the letter, adding that he anticipated "the final report will be released publicly with few redactions."

Horowitz noted that he did not anticipate a need to prepare or issue "separate classified and public versions of the report."

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"After we receive the final classification markings from the Department and the FBI, we will then proceed with our usual process for preparing a final report, including ensuring that appropriate reviews occur for accuracy and comment purposes," Horowitz wrote in the letter. "Once begun, we do not anticipate the time for that review to be lengthy."

The letter came as top Republicans on Wednesday demanded that Intelligence Community Inspector General (ICIG) Michael Atkinson explain why the watchdog hasn't said if it's investigating "a number of leaks of highly sensitive information" in recent years -- and released several previously unpublished texts and emails from since-fired FBI agent Peter Strzok, who oversaw the Russia probe.

Horowitz faulted the FBI last year for repeated violations of its media communications policy, noting that agents had received gifts from reporters and leaked regularly -- apparently even from phones at FBI headquarters in Washington, D.C.

For over a year and a half, Horowitz has been investigating alleged misconduct related to the FISA warrants delivered by the Foreign Intelligence Surveillance Court (FISC).

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The Justice Department and FBI obtained warrants in 2016 to surveil Trump adviser Carter Page. It's unclear, at this point, if Page was the only Trump official against whom the DOJ obtained a FISA warrant. Page told Fox News earlier this month he was "frustrated" he had not been interviewed in Horowitz's probe.

Partially redacted versions of the FBI's FISA warrant to surveil Page revealed that the FBI relied on a largely discredited dossier written by British ex-spy Christopher Steele that was funded by the Hillary Clinton campaign and Democratic National Committee. But, the FBI apparently obscured that fact in its warrant application, telling the secret court only that the dossier was prepared at the behest of an unidentified presidential campaign.

Additionally, it has emerged that Steele had communications with a State Department contact -- which were relayed to the FBI -- in which Steele claimed the Russians were running a "technical/human operation run out of Moscow targeting the election" and that "payments to those recruited are made out of the Russian Consulate in Miami."

There is no Russian consulate in Miami, a fact the State Department official, Deputy Assistant Secretary of State Kathleen Kavalec, emphasized in her notes. Additionally, Steele had suggested his client was "keen" to see his information come to light prior to Election Day.

Kavalec forwarded her notes to the FBI and other government officials several days before the FISA warrant was issued for Page.

Further, in its original FISA application and subsequent renewals, the FBI told the FISA court that it "did not believe" Steele was the direct source for a Yahoo News article implicating Page in Russian collusion. Instead, the FBI suggested to the court, the September 2016 article by Michael Isikoff was independent corroboration of the dossier.

But, London court records showed that contrary to the FBI's assessments, Steele briefed Yahoo News and other reporters in the fall of 2016 at the direction of Fusion GPS.

Additionally, Special Counsel Robert Mueller was unable to substantiate other key claims in the dossier, including that the Trump campaign employed hackers in the United States, that there was a compromising recording of the president in a hotel room, and that ex-Trump attorney Michael Cohen flew to Prague to build a conspiracy with hackers. Cohen has denied ever heading to Prague, and no public evidence has contradicted that claim.

Horowitz's highly anticipated report likely will spark new congressional investigations and deliver critical information to other federal reviews probing allegations of abuse by the Justice Department and the FBI.

“As soon as Horowitz is done with his review of the FISA warrant application, the counterintelligence investigation, the Trump campaign, we’ll have a hearing in public with Horowitz and we’ll call a bunch of witnesses,” Senate Judiciary Committee Chairman Lindsey Graham, R-S.C., said on Fox Business Network's "Sunday Morning Futures."

Last month, Horowitz submitted a draft of his report to Attorney General Bill Barr, who was reviewing the document.

President Trump -- who has the authority to declassify and release as much of the report as he wants -- has been hyping its forthcoming release. "The IG report is going to come out soon, and we’ll see what happens," the president told reporters last week, adding he's "waiting for the report like everybody else."

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"But, I predict you will see things that you don’t even believe, the level of corruption — whether it’s [James] Comey; whether it’s [Peter] Strzok and his lover, [Lisa] Page; whether it’s so many other people — [Andrew] McCabe; whether it’s President Obama himself," Trump charged.

He added: "Let’s see whether or not it’s President Obama. Let’s see whether or not they put that in."