Enlarge By Chip Somodevilla, Getty Images Robert Rubin, former chairman of the Executive Committee of the Board of Directors at Citigroup, prepares to testify before the Financial Crisis Inquiry Commission on Capitol Hill April 8, 2010.

"I'm particularly struck by how much the two of you did not know about what was going on within the organization. At the end of the day, you were the head guys," said Phil Angelides, the panel's chairman. "... The two of you in charge of this organization did not seem to have a grip on what was happening."

The executives — former CEO Charles Prince and Robert Rubin, former chairman of the board — said the handling of individual securities on Citi's books was left to lower-level executives. Prince, who resigned in November 2007 as the bank reported an epic write-down of $8 billion to $11 billion on subprime mortgage loans, opened the hearing with a personal apology for his role in the worst financial disaster since the Great Depression.

"I'm sorry the financial crisis had such a devastating impact for our country," Prince said. "I'm sorry about the millions of people, average Americans, who lost their homes. And I'm sorry that our management team, starting with me, like so many others, could not see the unprecedented market collapse that lay before us."

As the largest U.S. bank, with assets of $2.2 trillion, Citigroup was a financial player of global heft. But after suffering losses of about $50 billion on subprime securities it had believed were almost risk-free, the bank needed to be saved from collapse by Uncle Sam. In 2008, as part of a broader bailout of the financial system, the Treasury Department provided a $45 billion transfusion for Citi and guaranteed an additional $301 billion in assets.

Testifying under oath, Prince and Rubin defended the bank's internal system for monitoring risk. The bank, like many others on Wall Street, became complacent after a long period of robust growth and relied too heavily on assurances from credit-rating agencies such as Moody's and Standard & Poor's that securities linked to subprime mortgages were sound.

Prince was criticized for not reacting more quickly in 2007 as the global market for such securities began falling apart. And members of the bipartisan commission took him to task for an oft-repeated quote that has become part of financial crisis lore. That summer, as financial tremors escalated, Prince told a reporter: "As long as the music is playing, you've got to get up and dance."

The remark was later taken to represent a cavalier stance. But Thursday, Prince defended the comment, saying he had been referring to a different part of Citigroup's business — lending to private-equity firms — and not to the mortgage arena.

But it was Rubin, the former U.S. Treasury secretary who served at the time as chairman of the Citigroup board's executive committee, who absorbed the heaviest blows. The Wall Street veteran, former co-chairman of Goldman Sachs, was so influential in the 1990s that the blend of market-friendly policies favored by the Clinton administration came to be known as Rubinomics.

Rubin, who spent about a month as chairman of the board after Prince resigned and oversaw the search for a new CEO, testified that he had no management or operational responsibilities at Citi while the crisis grew. He described his role then as meeting with clients and foreign government officials and providing strategic advice to Prince. And he embedded his expression of regret in a broader catalog of failure involving regulators, ratings agencies, analysts and others, saying, "We all bear responsibility for not recognizing this (crisis), and I deeply regret that."

That left both Democrats and Republicans on the panel dissatisfied. Angelides, a former Democratic candidate for governor in California, noted that Rubin received $15 million in annual compensation and was often in contact with Prince several times a day. "Do you bear central responsibility for the near collapse, but for the U.S. government, of Citigroup?" he asked.

Ever unflappable, Rubin said the board's executive committee he headed in 2007 was an administrative body that wasn't a "substantive part of the decision-making process." And Prince jumped in to defend his former colleague, saying it was "absolutely incorrect" to suggest he bore special responsibility.