The Justice Department announced on Wednesday the formation of a task force to look into unsubstantiated allegations by President Trump that President Barack Obama and his aides ordered an investigation into the 2016 Trump campaign’s connections to Russia to destroy Mr. Trump.

The announcement, which came in an ambiguous, bare-bones statement on the department’s website, was a continuation of Mr. Trump’s campaign of retribution. It also represented yet another Trump pivot away from the political morass of the Jeffrey Epstein files in targeting Mr. Obama, whose presidency set off a wave of reactionary anger that helped propel Mr. Trump from a punchline to political dominance.

The move came hours after Tulsi Gabbard, the director of national intelligence, ramped up her attacks on Mr. Obama, releasing a document that she said undermined the conclusion of his intelligence agencies that Russia favored the election of Mr. Trump in 2016.

Ms. Gabbard said that after Mr. Trump’s first election, Mr. Obama ordered an intelligence analysis that was subject to “unusual directives” from him. She criticized that assessment as using unclear or unknown sources.

Under questions from reporters, she said Obama administration officials had led to a “yearslong coup and treasonous conspiracy” against Mr. Trump.

Asked if she thought Mr. Obama was implicated in criminal behavior, Ms. Gabbard said she had referred documents to the F.B.I.

“The evidence that we have found and that we have released directly point to President Obama leading the manufacturing of this intelligence assessment,” she said. “There are multiple pieces of evidence and intelligence that confirm that fact.”

The documents Ms. Gabbard has produced, both Wednesday and last week, show that Obama administration officials wanted to complete a review before they left office and put pressure on the intelligence agencies to work quickly, but there is no evidence of criminal behavior.

The document released on Wednesday was a report that the House Intelligence Committee originally drafted in 2017, when Republicans led the panel. The report took issue with the conclusion reached in December 2016 that President Vladimir V. Putin of Russia had favored Mr. Trump.

Only Republicans on the committee participated in the drafting of the 2017 report and revisions in 2020.

The new material provides some interesting insights into the development of the review of Russian activity by American spy agencies, and the debate over their assessment. But none of the new information changes the fundamental view that Russia meddled in the election and that Mr. Putin hoped to damage Hillary Clinton, the Democratic nominee.

Ms. Gabbard has won praise from Mr. Trump for her investigation into the intelligence findings and spoke at length about how the 2016 assessment was part of a witch hunt against him. The president has been under sharp criticism for his handling of documents related to the disgraced financier Jeffrey Epstein, and his attacks on the Obama administration appear to be part of a distract-and-deflect strategy.

The report was released with relatively few redactions, prompting criticism from Democrats.

“The desperate and irresponsible release of the partisan House intelligence report puts at risk some of the most sensitive sources and methods our intelligence community uses to spy on Russia and keep Americans safe,” said Senator Mark Warner of Virginia, the top Democrat on the Senate Intelligence Committee.

Officials familiar with the matter said that another, more heavily redacted version took care to hide more information about U.S. sources and had been considered for release. Ms. Gabbard said on social media that Mr. Trump had declassified the report.

Kash Patel, now Mr. Trump’s F.B.I. director, was a key author of the report released on Wednesday, according to officials.

The House report found that most of the judgments made by the intelligence community in 2016 were sound. But it argued that the work was rushed, as a recent tradecraft analysis by the C.I.A. also found. The assessment that Mr. Putin had favored Mr. Trump did not follow the “professional criteria” of the other findings, the House report said.

The findings were at odds with a bipartisan series of Senate reports from a committee that included Marco Rubio, then a Republican senator from Florida and now Mr. Trump’s secretary of state. The Senate Intelligence Committee affirmed the work of the C.I.A. and the other intelligence agencies on the 2016 assessment.

Mr. Warner said Wednesday that the bipartisan effort by the Senate included a yearslong investigation that went through millions of documents and 200 witness interviews. It concluded, he said, that “Russia launched a large-scale influence campaign in the 2016 election to help then-candidate Trump.”

John H. Durham, a special prosecutor appointed by Attorney General William P. Barr during Mr. Trump’s first term, also failed to find any evidence undermining the intelligence agencies’ conclusions.

But the House report said the judgment about Mr. Putin’s preference was based on a single source who was biased against the Russian government. The raw intelligence was fragmentary and lacked context, the report added.

The detailed discussion of the source has not been made public before, although the U.S. decision to extract and relocate him, first to Virginia, has become public. Russia officials made the source’s identity public and said he was an aide to a senior Russian official.

The 2017 report portrays the information as incomplete and subject to interpretation, pointing to a single piece of intelligence from the man that said Mr. Putin had decided to leak emails stolen from the Democratic National Committee because Mrs. Clinton had better odds of the election and Mr. Trump, “whose victory Putin was counting, most likely would not be able to pull off a convincing victory.”

But current and former American officials pushed back on the characterization of the source’s intelligence, saying he was well placed and had provided sound information to the United States on Mr. Putin’s intentions.

While details about the debate over the source are new, the overall view of the House Intelligence Committee was well known, and members frequently took issue with the finding. But the full report with details of the C.I.A.’s work on the 2016 intelligence assessment has not been released.

Attacking the conclusions of the 2016 assessment that Russia sought to denigrate Mrs. Clinton and help Mr. Trump has been a hobby horse of some of the president’s supporters. Republicans have long taken particular aim at the idea that the Kremlin favored Mr. Trump, arguing instead that Russia was simply trying to sow chaos or undermine democratic institutions.

Ms. Gabbard echoed that position on Wednesday.

The attacks on the documents have intensified in recent weeks as first the C.I.A. and then Ms. Gabbard’s office have raised questions about the effort.

While Mr. Trump’s Republican supporters criticized the assessment during his first term, the president focused much of his ire on Robert S. Mueller III, the former F.B.I. director appointed to investigate any ties between the Trump campaign and Russian officials.

The newly released House document also takes a close look at the role that a dossier prepared by a former British intelligence officer, Christopher Steele, played in the 2016 assessment.

Trump administration officials have maintained that the 2016 intelligence review was tainted by unverified information in the so-called Steele dossier. A classified annex to the report mentioned the dossier, but former officials said the C.I.A. did not take it seriously and did not allow it to influence their assessment.

Few if any of the claims in Mr. Steele’s work about Mr. Trump have been verified in the ensuing years.

In interviews this week, former officials insisted the Steele dossier did not influence the findings of the 2016 assessment. But the House report took issue with that, noting that in one of the bullet points in the original, classified version, the assessment referred readers to the annex discussing the dossier. The House report said the two-page annex summarizing the dossier “misrepresented the significance and credibility” of Mr. Steele’s work.

The dossier “was written in an amateurish conspiracy and political propaganda tone that invited skepticism, if not ridicule, over its content,” the report continued.

The House review also said one C.I.A. officer said he confronted John O. Brennan, the agency’s director at the time, with the flaws of the dossier. Mr. Brennan, according to the House report, acknowledged the flaws but added, “doesn’t it ring true.”

Mr. Brennan, who emerged as one of the sharpest critics of Mr. Trump, has long denied that the dossier colored the assessment and said that he backed C.I.A. officers who wanted it kept out of the main body. He has said he placed the dossier in the annex at the insistence of the F.B.I.

Former Obama administration officials acknowledged in hindsight that including the unverified dossier in the annex was a mistake, given the justifiable criticisms Republicans had of Mr. Steele’s assertions. But the officials said the F.B.I. felt it had no choice but to include it in the annex to avoid appearing as if they were hiding something from Mr. Trump.

C.I.A. officials wanted to be sure the F.B.I. signed on to the overall assessments, and they felt that the bureau would do that only if the annex was included, former officials said.

Ms. Gabbard has said she wants to end the weaponization of intelligence. She has condemned politicians for what she sees as the use of selective bits of intelligence against their opponents.

While she has portrayed the release of the documents as a corrective to the errors and missteps of the Obama administration, former officials and even some allies of Ms. Gabbard have said her effort to throw a lifeline to Mr. Trump is an example of the very politicization she has vowed to stamp out.