WASHINGTON — When the credit crisis struck last year, federal regulators pumped tens of billions of dollars into the nation's leading financial institutions because the banks were so big that officials feared their failure would ruin the entire financial system.

WASHINGTON — When the credit crisis struck last year, federal regulators pumped tens of billions of dollars into the nation's leading financial institutions because the banks were so big that officials feared their failure would ruin the entire financial system.

Today, the biggest of those banks are even bigger.

The crisis may be turning out very well for many of the behemoths that dominate U.S. finance. A series of federally arranged mergers safely landed troubled banks on the decks of more stable firms. And it allowed the survivors to emerge from the turmoil with strengthened market positions, giving them even greater control over consumer lending and more potential to profit.

J.P. Morgan Chase, an amalgam of some of Wall Street's most storied institutions, now holds more than $1 of every $10 on deposit in this country. So does Bank of America, scarred by its acquisition of Merrill Lynch and partly government-owned as a result of the crisis, as does Wells Fargo, the biggest West Coast bank. Those three banks, plus government-rescued and -owned Citigroup, now issue one of every two mortgages and about two of every three credit cards, federal data show.

A year after the near-collapse of the financial system last September, the federal response has redefined how Americans get mortgages, student loans and other kinds of credit and has made a national spectacle of executive pay. But no consequence of the crisis alarms top regulators more than having banks that were already too big to fail grow even larger and more interconnected.

"It is at the top of the list of things that need to be fixed," said Sheila Bair, chairman of the Federal Deposit Insurance Corp. "It fed the crisis, and it has gotten worse because of the crisis."

Regulators' concerns are twofold: that consumers will wind up with fewer choices for services and that big banks will assume they always have the government's backing if things go wrong. That presumed guarantee means large companies could return to the risky behavior that led to the crisis if they figure federal officials will clean up their mess.

This problem, known as "moral hazard," is partly why government officials are keeping a tight rein on bailed-out banks — monitoring executive pay, reviewing sales of major divisions — and it is driving the Obama administration's efforts to create a new regulatory system to prevent another crisis. That plan would impose higher capital standards on large institutions and empower the government to take over a wide range of troubled financial firms to wind down their businesses in an orderly way.

"The dominant public policy imperative motivating reform is to address the moral hazard risk created by what we did, what we had to do in the crisis to save the economy," Treasury Secretary Tim Geithner said in an interview.

The worry for consumers is that the bailouts skewed the financial industry in favor of the big and powerful. Fresh data from the FDIC show that big banks have the ability to borrow more cheaply than their peers because creditors assume these large companies are not at risk of failing. That imbalance could eventually squeeze out smaller competitors. Already, consumers are seeing fewer choices and higher prices for financial services, some senior government officials warn.

Those mergers were largely the government's making. Regulators pushed failing mortgage lenders and Wall Street firms into the arms of even bigger banks and handed out billions of dollars to ensure that the deals would go through. They say they reluctantly arranged the marriages. Their aim was to dull the shock caused by collapses and prevent confidence in the U.S. financial system from crumbling.

Officials waived long-standing regulations to make the deals work. J.P. Morgan Chase, Bank of America and Wells Fargo were each allowed to hold more than 10 percent of the nation's deposits despite a rule barring such a practice. In several metropolitan regions, these banks were permitted to take market share beyond what the Department of Justice's antitrust guidelines typically allow, Federal Reserve documents show.

"There's been a significant consolidation among the big banks, and it's kind of hollowing out the banking system," said Mark Zandi, chief economist of Moody's Economy.com. "You'll be left with very large institutions and small ones that fill in the cracks. But it'll be difficult for the mid-tier institutions to thrive."

"The oligopoly has tightened," he added.

The administration's regulatory reform plan takes aim at this problem by penalizing banks for being big. It would require large institutions to hold more capital and pay higher regulatory fees, as well as allow the government to liquidate them in an orderly way if they begin to fail. The plan also seeks to bolster nontraditional channels of finance to create competition for large banks. If Congress approves the proposal, Geithner said, it would be clear at launch which financial companies would face these measures.

Economists and officials debate whether these steps would address the too-big-to-fail problem. Some say, for instance, that determining the precise amount of capital big financial companies should hold in their reserves will be difficult.

Geithner acknowledged that difficulty but said the administration would probably lean toward being more strict. Taken together, the combination of reforms would be a powerful counterbalance to big banks, he said.