NEW YORK – Vikram Pandit, who abruptly resigned last week as chief executive officer of Citigroup Inc., was among the most vocal critics of shadow banking, the lightly regulated lending that can mask risk in the financial system. He was also among the kings of the business.

Under Pandit, Citigroup arranged more than $7 billion of collateralized loan obligations in the U.S. this year through September, three times as much as the same period in 2011 and more than any other lender, according to data compiled by Bloomberg and Morgan Stanley. The bank also caters to money-market funds, managed-share sales in mortgage real estate investment trusts and runs a stable of internal credit funds.

All are part of a shadow-banking system that offers complex forms of credit and that led and leading to billions of dollars in losses during the financial crisis. While regulators say they’re scrutinizing this lending to prevent another calamity, banks including Citigroup, Goldman Sachs and JPMorgan Chase are among its biggest enablers.

“I agree with Mr. Pandit that financial reform really hasn’t dealt with shadow banking,” said Erik Gerding, a law professor who specializes in banking regulation. “But I disagree in that large financial institutions, large investment banks, are really key players in the shadow-banking network.”

Pandit’s departure and that of President John P. Havens, announced a day after the bank reported a surprise quarterly profit, removes a leadership team that navigated the firm through the 2008 global credit crisis, when taxpayers rescued it from collapse with a $45 billion bailout. Citigroup was forced to buy back $25 billion of mortgage-backed securities because of commitments made by shadow-banking conduits the company kept off its balance sheet, contributing to a $27.7 billion loss.

Regulators targeted traditional banks after the worst financial crisis since the Great Depression. Lenders such as New York-based Citigroup have had to boost capital to protect against future losses, comply with new rules for derivatives and exit risky trading businesses.

Pandit, 55, criticized lawmakers for neglecting unregulated entities while saddling lenders such as his with restrictions. Investors are “flowing” into shadow banks as a result, a “major concern that should trouble us all,” he said in Singapore in August. Those views echo a June report by the Institute of International Finance, which represents more than 450 financial firms, urging regulators to scrutinize risks.

Shadow-banking entities include money-market funds, CLOs, credit hedge funds and asset-backed commercial paper conduits, according to a 2010 Federal Reserve Bank of New York staff report. They provide “sources of inexpensive funding for credit by converting opaque, risky, long-term assets into money-like and seemingly riskless short-term liabilities,” the authors wrote in an abstract of the report.

The industry has escaped the reach of new laws despite its size, Pandit has said. Shadow-banking assets in 11 countries including the United States have more than doubled since 2002 to $51 trillion, an amount equal to about half of total bank assets in those nations, according to a 2011 report by the Financial Stability Board, which coordinates the work of regulators, central bankers and policy makers.

The lack of oversight of these financial intermediaries has created an unchecked market that resembles a chaotic street scene in his native India, Pandit said at a conference in Washington in September 2011.

“I’m reminded of towns in India in which every house, on the inside, is as clean and orderly as you can imagine,” said Pandit, who was born in Nagpur, a city in central India. “While just beyond the door, chaos and disorder reign.”

Just beyond the door lies profit as well.

Citigroup, the third-largest U.S. bank by assets, dominates the market for arranging CLOs, entities that bundle high-yield loans and slice them into securities of varying risk and return. As the arranger of about 25 percent of CLOs issued this year, the firm helps managers structure and market the deals and earns fees for its efforts.

CLOs are among shadow-banking products that are difficult to value and whose liquidity can evaporate quickly, as happened during the financial crisis, Gerding said. They and other such instruments can expose sponsors to litigation risks if a product collapses and investors seek compensation, he said.

New regulations for U.S. lenders haven’t dealt with the “implicit support” they provide to the shadow-banking system, Federal Reserve Governor Daniel Tarullo said last week.

Support for shadow-banking products led to losses in the past. Citigroup bailed out investors in distressed special investment vehicles, or SIVs, in 2008, soon after Pandit took the top job.