The F.B.I. never tried to place undercover agents or informants inside the Trump campaign, a highly anticipated inspector general’s report is expected to find.

Credit...Tom Brenner for The New York Times

WASHINGTON — The Justice Department’s inspector general found no evidence that the F.B.I. attempted to place undercover agents or informants inside Donald J. Trump’s campaign in 2016 as agents investigated whether his associates conspired with Russia's election interference operation, people familiar with a draft of the inspector general’s report said.

The determination by the inspector general, Michael E. Horowitz, is expected to be a key finding in his highly anticipated report due out on Dec. 9 examining aspects of the Russia investigation. The finding also contradicts some of the most inflammatory accusations hurled by Mr. Trump and his supporters, who alleged not only that F.B.I. officials spied on the Trump campaign but also at one point that former President Barack Obama had ordered Mr. Trump’s phones tapped. The startling accusation generated headlines but Mr. Trump never backed it up.

The finding is one of several by Mr. Horowitz that undercuts conservatives’ claims that the F.B.I. acted improperly in investigating several Trump associates starting in 2016. He also found that F.B.I. leaders did not take politically motivated actions in pursuing a secret wiretap on a former Trump campaign adviser, Carter Page — eavesdropping that Mr. Trump’s allies have long decried as politically motivated.

But Mr. Horowitz will sharply criticize F.B.I. leaders for their handling of the investigation in some ways, and he unearthed errors and omissions when F.B.I. officials applied for the wiretap, according to people familiar with a draft of the report. The draft contained a chart listing numerous mistakes in the process, one of the people said.

Mr. Horowitz concluded that the F.B.I. was careless and unprofessional in pursuing the Page wiretap, and he referred his findings in one instance to prosecutors for potential criminal charges over the alteration of a document in 2017 by a front-line lawyer, Kevin Clinesmith, 37, in connection with the wiretap application.

Mr. Horowitz’s mixed bag of conclusions is likely to give new ammunition to both Mr. Trump’s defenders and critics in the long-running partisan fight over the Russia investigation. Last week, Mr. Trump described the coming report in a phone interview with “Fox & Friends” as potentially “historic” and predicted “perhaps the biggest scandal in the history of our country.”

A spokeswoman for Mr. Horowitz declined to comment. The people familiar with the inquiry cautioned that the draft report was not final. The New York Times has not reviewed the draft, which could include other significant findings.

Mr. Trump has long chafed at the Russia investigation, which overshadowed the first years of his presidency. Ultimately, the special counsel who took over the Russia inquiry, Robert S. Mueller III, found insufficient evidence to charge any Trump associates with conspiring with Russia’s interference.

But the president’s allies have seized on the F.B.I.’s conduct in opening the inquiry as potentially problematic. Attorney General William P. Barr prompted alarm among defenders of the F.B.I. by accusing the bureau this year of spying on the campaign.

The F.B.I. director, Christopher A. Wray, who was appointed in 2017, has said he would not use the term spying to describe F.B.I. activities in 2016. The Mueller report reaffirmed the factors that the F.B.I. used to open its investigation, and Mr. Horowitz’s findings are also said to show that the F.B.I. acted properly in opening the inquiry.

F.B.I. officials started the investigation, code-named Crossfire Hurricane, in July 2016 after learning that a Russian intermediary had offered information that could damage Hillary Clinton to a Trump campaign aide, George Papadopoulos. The F.B.I. eventually began looking at four Trump campaign advisers who had ties to Russia, including Mr. Papadopoulos, and as law enforcement and intelligence officials were realizing the extent of the Kremlin’s ongoing campaign to sabotage the election.

The F.B.I. was cognizant of being seen as interfering with a presidential campaign, and former law enforcement officials are adamant that they did not investigate the Trump campaign organization itself or target it for infiltration. But agents had to investigate the four advisers’ ties with Russia, and the people they did scrutinize all played roles in the Trump campaign.

Mr. Trump and his allies have pointed to some of the investigative steps the F.B.I. took as evidence of spying, though they were typical law enforcement activities. For one, agents had an informant, an academic named Stefan A. Halper, meet with Mr. Page and Mr. Papadopoulos while they were affiliated with the campaign. The president decried the revelation as an “all time biggest political scandal” when it emerged last year.

The F.B.I. did have an undercover agent who posed as Mr. Halper’s assistant during a London meeting with Mr. Papadopoulos in August 2016. And indeed, another Trump adviser, Peter Navarro, reportedly pushed Mr. Halper for an ambassadorship in the Trump administration.

Mr. Halper turned down the job and told the F.B.I. that Mr. Navarro had made the overture, according to a person familiar with the offer.

Mr. Horowitz found no evidence that Mr. Halper tried to infiltrate the Trump campaign itself, the people familiar with the draft report said, such as by seeking inside campaign information or a role in the organization. The F.B.I. also never directed him to do so, former officials said. Instead, Mr. Halper focused on eliciting information from Mr. Page and Mr. Papadopoulos about their ties to Russia.

Mr. Barr has suggested that the F.B.I. assigned other informants as well to figure out whether any Trump associates were working with the Russians. The F.B.I. gave Mr. Horowitz’s team extraordinary access to its informant database, and his investigators examined other F.B.I. informants with possible ties to the Trump campaign.

In each case, they found that the F.B.I. had not deployed those people to gather information on the Trump campaign itself, the people said.

It is also possible that the F.B.I. received unsolicited material from inside the Trump campaign; outsiders often submit potential evidence to the bureau that agents did not seek. But it is not clear whether Mr. Horowitz uncovered any such instances.

Mr. Horowitz will also undercut another claim by Trump allies — that the Russian intermediary who promised dirt to Mr. Papadopoulos, a Maltese professor named Joseph Mifsud, was an F.B.I. informant. Mr. Papadopoulos has helped spread that claim; he contends without evidence that the F.B.I. or the C.I.A. set him up to derail Mr. Trump’s campaign.

Mr. Papadopoulos served 12 days in prison last year on a conviction of lying to the F.B.I. about his contacts with Mr. Mifsud. Agents said his falsehoods hampered their ability to interrogate Mr. Mifsud, who was briefly in the United States but later left the country, out of the reach of the F.B.I., and disappeared from public view.

The report is also expected to debunk another theory of Trump allies: that the F.B.I. relied on information to open the investigation from a British former spy, Christopher Steele, himself a onetime bureau informant who compiled a dossier of damaging, unverified information on Mr. Trump.

The F.B.I. did cite the dossier to some extent to apply for the wiretap on Mr. Page. The inspector general will fault the F.B.I. for failing to tell the judges who approved the wiretap applications about potential problems with the dossier, the people familiar with the draft report said. F.B.I. agents have interviewed some of Mr. Steele’s sources and found that their information differed somewhat from his dossier.

Mr. Horowitz plans to say that the wiretap application, which referenced Mr. Papadopoulos, should have also included a statement he made to the undercover agent in London that could be seen as exculpatory or self-serving, the people familiar with the draft report said. Mr. Papadopoulos said at the time that he had nothing to do with Russia and knew no one else who did, he recounted in a book he has written.

Though a wiretap itself is an intrusive investigative tool, F.B.I. officials obtained a wiretap on Mr. Page after he had left the Trump campaign.

In addition, the inspector general examined Mr. Steele’s contacts with Bruce G. Ohr, a Justice Department official and an expert on Russian organized crime. Mr. Ohr, himself a target of Mr. Trump’s ire, spoke with Mr. Steele several times after the F.B.I. terminated its relationship with him in the fall of 2016 because he spoke with a reporter about his concerns about Mr. Trump. Mr. Ohr relayed information from those conversations to the bureau.

Mr. Horowitz is expected to criticize Mr. Ohr for keeping his meetings with Mr. Steele from his superiors.

The report will mark the end of one chapter of the Justice Department’s scrutiny of the F.B.I.’s handling of the Russia investigation, though the saga is ongoing. Mr. Barr has assigned the United States attorney for Connecticut, John H. Durham, to also examine the origins of the inquiry and the government’s collection of intelligence involving the Trump campaign’s interactions with Russians.

Michael S. Schmidt contributed reporting.