WASHINGTON — Jon Corzine once saw a boutique brokerage called MF Global as his best hope to rescale the heights of Wall Street he'd once occupied as head of Goldman Sachs.

Now, MF Global is bankrupt. And Corzine faces a lifetime ban from the futures industry.

On Thursday, federal regulators sued Corzine, a onetime U.S. senator and governor of New Jersey. They allege that he was responsible for the misuse of customer money while CEO of MF Global, which collapsed in 2011.

A civil lawsuit filed in Manhattan by the Commodity Futures Trading Commission seeks to restrict Corzine's ability to trade investments and demands he pay unspecified penalties.

The suit charges that MF Global violated U.S. laws in the weeks before it collapsed by using customer funds to support its own trading operations. About $1.2 billion in customer money vanished when the firm collapsed.

Corzine bore responsibility for the unlawful acts by MF Global because he controlled the firm and its holdings and "either did not act in good faith or knowingly induced these violations," the lawsuit says.

In a conference call with reporters, CFTC Enforcement Director David Meister said Corzine failed to do enough to "prevent the firm from dipping into customers' funds to stay afloat."

MF Global has agreed to pay a $100 million penalty as part of a settlement announced Thursday. The money will come from bankruptcy proceedings.

Corzine has disputed the allegations by the CFTC, which regulated New York-based MF Global. He did so again Thursday through his lawyers.

"Mr. Corzine did nothing wrong, and we look forward to vindicating him in court," attorney Andy Levander said in a statement.

James Giddens, the court-appointed trustee overseeing MF Global's bankruptcy, called the settlement with the CFTC "appropriate." He said the $100 million penalty will be paid only after the firm's customers and creditors have received all their claims.

The CFTC also filed civil charges against Edith O'Brien, the firm's former assistant treasurer. Last year, O'Brien was summoned to a congressional hearing into what happened in MF Global's final days. She declined to answer questions, invoking her Fifth Amendment right against self-incrimination.

Attorneys for O'Brien didn't immediately return a call seeking comment Thursday.

The lawsuit seeks to bar Corzine and O'Brien from working for any firms that trade commodities or other investments regulated by the CFTC. Corzine and O'Brien would also be barred from trading any such investments on their own. They could still trade stocks and bonds.

Thursday's lawsuit is striking in that regulators have seldom charged individuals with financial crisis-era misdeeds. They have instead imposed fines and penalties against companies, often with no one having to admit blame.

Nearly 90 percent of the money belonging to the firm's U.S. customers has been recovered. Many farmers, ranchers and business owners used futures contracts through MF Global to hedge their risks against fluctuating crop prices. A futures contract allows someone to agree with someone else to buy or sell something — corn, say, or gold — at a set price at some point in the future.

The CFTC need not show in court that Corzine personally authorized the use of customer money, said Anthony Sabino of the New York law firm Sabino & Sabino, which specializes in white-collar crime. Top executives can be liable for "failure to maintain internal controls" or "failure to supervise," Sabino said.

Under a 2002 anti-corporate fraud law — which Corzine co-wrote as a U.S. senator — CEOs of public companies must personally certify the accuracy of their company's financial statements.

"When the Titanic went down, you didn't blame the cook; you didn't blame the guy in the engine room," Sabino said. "You blamed the captain. And Corzine is the captain of the ship called MF Global."

The CFTC has "a very substantial case" against Corzine and MF Global, Sabino said.

Robert Mintz, a former federal prosecutor, predicted that Corzine and the CFTC would eventually settle but not before a drawn-out battle.

That the CFTC filed suit against such a major defendant signals confidence that they have a strong case, he suggested.

"A defeat in a case like this, in such a high-profile setting, would come at some cost to the reputation of the agency," said Mintz, now at McCarter & English in New Jersey.

It isn't clear how much money Corzine is worth. He spent roughly $100 million of his fortune to win a U.S. Senate seat and the New Jersey governorship. In 2005, the last full year that he was a U.S. senator, he was estimated to be worth between $125 million and $175 million.

MF Global sought bankruptcy protection in 2011 after a disastrous bet on European countries' debt. Under Corzine's leadership, the firm bet $6.3 billion on bonds issued by Italy, Spain and other nations with deeply troubled financial systems. Those bonds plummeted in value in the weeks before MF Global's failure as fears intensified that some European countries might default.

The firm's $41 billion bankruptcy was the eighth-largest in U.S. history. It was also the first collapse of a Wall Street firm since the 2008 financial crisis ended. Critics have long complained that regulators have failed to aggressively pursue much bigger financial firms, whose high-risk bets nearly toppled the financial system.

Corzine, 66, had been a CEO of Wall Street powerhouse Goldman Sachs before entering politics in 2000. He served as a Democratic U.S. senator from New Jersey and later governor of the state. He took the top job at MF Global in March 2010 after losing his 2009 bid for re-election as governor to Chris Christie.

MF Global was a small commodities broker when Corzine arrived. His vision was to transform the firm into a full-scale investment bank, similar to Goldman. The CFTC's lawsuit says he sought to do so by generating revenue from aggressive trading strategies.

The plan worked for a while even as the firm's investments grew increasingly risky, the lawsuit said. In the second half of 2011, its investments put heavy strains on its cash flow and capital. By October 2011, the lawsuit says, sources of cash were drying up.

Corzine and other employees communicated with one another, by email and sometimes on recorded phone lines, about the firm's "dire situation," the lawsuit says.

It says a treasurer of the firm's parent company, MF Global Holdings Ltd., told a chief financial officer and another employee in a recorded conversation on Oct. 6, 2011, that "we have to tell Jon that enough is enough. We need to take the keys away from him."

Corzine "disparagingly nicknamed the Global treasurer 'the Gravedigger,'" the lawsuit says

Corzine stepped down as MF Global chief in November 2011, a few days after the firm filed for bankruptcy protection.

Three reports on MF Global's collapse, by a House panel and two court-appointed trustees, placed most of the blame on Corzine. It said his risky strategies caused the failure.

Shareholders of MF Global have sued Corzine and other top managers. The investors say they lost about $585 million in just a week as the firm foundered. They accuse MF Global and the executives of making false and misleading statements about the firm's financial strength.

Giddens, the trustee, also joined a lawsuit filed by MF Global customers against Corzine and the other top executives.

Corzine testified at three hearings of House and Senate committees in December 2011 after lawmakers subpoenaed him. It was a rare sight in Washington: A former member of Congress being called by former colleagues to testify publicly about potential violations of law.

Corzine's testimony offered little to satisfy lawmakers or MF Global customers who lost money. Yet his explanations would be hard to disprove, legal experts said.

He said he never intended to "misuse" client money or to order anyone else to do so. Corzine also rebuffed an assertion that he knew about customer money that might have been transferred to a European affiliate just before MF Global collapsed.

O'Brien, the former assistant treasurer, was subpoenaed to testify at a hearing last year about an email she sent that appeared to contradict testimony from Corzine. The email said Corzine ordered a transfer of customer money to cover an overdraft in the firm's bank account in London.

"On the advice of counsel," she told Congress, "I respectfully decline to answer based on my constitutional right."