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Congressional investigators on Wednesday took aim at a former colleague, Jon S. Corzine, blaming the onetime senator’s risk-taking at MF Global for accelerating the brokerage firm’s demise.

In excerpts from a broader MF Global report that is to be released on Thursday, Republican members of a Congressional panel outlined a withering critique of Mr. Corzine’s 19-month reign at the firm. Mr. Corzine, a former Democratic senator and governor from New Jersey, resigned as MF Global’s chief executive last fall after the firm raided customer accounts during a futile fight for survival.

The attack on Mr. Corzine, leveled by Republicans on the oversight panel of the House Financial Services Committee, appeared to delineate political battle lines that have emerged after MF Global’s collapse. Democratic members declined to endorse the report, saying they needed additional time to study the findings.

Mr. Corzine could seize on the uncertainty. The fractured support offered his backers an avenue for dismissing the report as a political attack on the former Democratic politician.

But Congressional officials noted on Wednesday that Democrats had supported large swaths of the report and even contributed changes to the final draft. The report, the officials said, offers an unbiased lens for viewing the firm’s final days.

While lawmakers avoided blaming Mr. Corzine directly for the missing customer money, sidestepping whether a crime was committed, they argued that his fixation with taking risk helped topple the firm. The report labeled Mr. Corzine the “de facto chief trader,” an unusual title for a top executive.

“Choices made by Jon Corzine during his tenure as chairman and C.E.O. sealed MF Global’s fate,” Representative Randy Neugebauer, a Republican from Texas who is overseeing the report as chairman of the oversight panel, said in a statement.

In a series of potential missteps, the report said, Mr. Corzine missed warning signs about MF Global’s weak liquidity. Citing “a dereliction of his duty,” the report claimed that he had left customers vulnerable to the invasion of their accounts.

The report further asserts that Mr. Corzine was the architect of a $6.3 billion bet on European debt — a trade so big it spooked the markets and led to a run on the firm. When subordinates challenged Mr. Corzine’s European gamble, according to the report, he imposed an “authoritarian atmosphere” in which he ejected the aides and installed sympathetic executives he knew from his days at Goldman Sachs.

Even as the findings made a case for civil and regulatory action, the report shed little new light on Mr. Corzine’s actions and hardly chipped away at his legal defense. Federal authorities have all but officially removed the darkest cloud looming over Mr. Corzine: the threat of criminal charges.

In a statement, Steven Goldberg, a spokesman for the former chief executive, noted that lawmakers “apparently did not find any evidence that Mr. Corzine acted in bad faith or engaged in any intentional wrongdoing.” Mr. Goldberg added, “Mr. Corzine disagrees strongly with several of the assertions” in the report.

“At all times Mr. Corzine acted in good faith and did what he believed was necessary to turn around MF Global,” he said.

Mr. Corzine’s supporters have noted that his bet on European debt ultimately proved profitable for the firms that inherited the positions. Mr. Corzine, the supporters say, placed the wager to re-energize a firm that faced extinction after five consecutive quarters of losses that predated his tenure.

The excerpts divulged on Wednesday offer a preview of a long-awaited Congressional report. The House panel’s full findings, built on roughly 50 witness interviews and an analysis of more than 243,000 documents, are expected to strike at an array of regulatory and management failures that led up to MF Global’s bankruptcy in October 2011.

The House panel’s ranking Democrat, Michael Capuano of Massachusetts, said he would soon release “an addendum” to the Republican report.

“While I agree with a number of the report’s observations and recommendations, others require additional commentary,” Mr. Capuano said in a statement.

The report is the latest chapter in the MF Global story.

Farmers and ranchers, who traded futures contracts through MF Global to protect themselves from the price swings of their crops, have recouped about 82 percent of their money but are still owed millions of dollars.

Regulators continue to investigate how MF Global improperly transferred about $1 billion in customer money to pay its own bills. The Commodity Futures Trading Commission could still file a civil enforcement action charging Mr. Corzine with failing to supervise the employees who tapped the customer accounts. The Securities and Exchange Commission, according to people briefed on the matter, is also building potential civil cases surrounding the firm’s public disclosures.

But federal investigators do not expect to file criminal charges against top executives, said the people briefed on the matter, who spoke on the condition of anonymity because the investigations are private. The investigators, citing internal e-mails, have concluded that a state of chaos and sloppy recordkeeping caused the money to vanish. An e-mail reviewed by The New York Times shows that an MF Global employee had explicitly assured Mr. Corzine that money transferred on the final day of business belonged to the firm, not customers.

Lawmakers were not satisfied. They called Mr. Corzine to Washington three times last year to explain the missing money. In unwavering testimony, Mr. Corzine explained that he had never intended to authorize the misuse of customer money.

The passages released on Wednesday do not contradict his testimony. Instead, they detail his struggle to steer the firm out of crisis.

Fresh from a campaign loss for a second term as governor, Mr. Corzine took control of MF Global in March 2010. He hoped to shift MF Global from a sleepy firm that matched buyers and sellers of commodities into a miniature Goldman Sachs.

He did not, however, heed warnings that the firm’s internal risk controls were outdated. The firm’s failure to manage its liquidity put customers at risk, according to the report.

Mr. Corzine, the report said, also insulated his trading from review by keeping the European debt holdings off the firm’s balance sheet. When MF Global’s chief risk officer balked at an escalation of the position, the report said, Mr. Corzine sidelined the official. He later hired a chief risk officer who largely supported the trade. He also tapped Bradley Abelow, a former Goldman employee who had been Mr. Corzine’s aide in the governor’s mansion, as the firm’s chief operating officer.

“Corzine dramatically changed MF Global’s business model,” Mr. Neugebauer said, “without fully understanding the risks associated with such a radical transformation.”