Dimon, appearing on Capitol Hill on Tuesday for the second time in a week, again apologized for the loss but declined to accept personal responsibility, including the notion that he should offer to have his pay docked.

"My compensation is 100 percent up to my board," Dimon told the House Financial Services Committee. "They will do what they see as appropriate... I can't tell my board what to do."

Dimon on Tuesday mounted a defense against potential allegations of wrongdoing, saying he relied upon the people around him when in April he dismissed as a "tempest in a teapot" media reports that a London-based JPMorgan trader had amassed an outsized position that prompted hedge funds to bet against it.

It was not until May 10 that Dimon revealed on a conference call that the London office had so badly botched a hedging strategy that it had so far produced $2 billion in losses.

During the call, he divulged for the first time that the Chief Investment Office in London had changed its internal models in way that had understated its risk-taking.

"We disclosed what we knew when we knew it," Dimon told lawmakers on Tuesday.

He also said he believed it to be true when he certified JPMorgan's annual regulatory filing in February that said the bank had adequate risk controls in place.

"I believed at that time that the risk controls at the CIO were properly being done," he said, referring to the Chief Investment Office in London responsible for the trading loss.

JPMorgan's trading loss has raised questions about whether regulators and Wall Street executives have a good handle on banking giants which only got bigger during the 2007-2009 financial crisis by absorbing their fallen rivals.

RISK CHANGE

JPMorgan's crew of regulators appeared before the House committee ahead of Dimon, and gave more details about their investigations into the trading loss.

Securities and Exchange Commission Chairman Mary Schapiro said her agency is looking at whether JPMorgan misled investors in its April earnings statements by failing to disclose a change to its value-at-risk (VaR) model.

The VaR is a figure commonly used to judge the potential loss on a portfolio.

JPMorgan's CIO office changed its model in January in a way that disguised a doubling in its VaR and gave its traders more leeway to make risky bets.

During an April 13 call with analysts, Dimon downplayed media reports about the CIO's risk-taking.

Schapiro told the lawmakers "the area we're focused on and concerned about is a change with respect to the VaR model they used for their earnings release on April 13 that had the effect, yes, of understating the value-at-risk."

"If you choose to speak, you absolutely must speak truthfully and completely and not allow yourself to leave any kind of misleading impression from the information that you are putting out," Schapiro said.

She said it is hard to say what sort of financial penalty JPMorgan could face, but said the SEC has a large number of potential sanctions.

An analyst report released on Tuesday compared JPMorgan's risk disclosure practices against its rivals, and concluded that the bank gives investors a murkier view of its risk.

TOO BIG?

Dimon's testimony on Tuesday followed his appearance last Wednesday before the Senate Banking Committee, where senators were mostly deferential.

A few members of the House Financial Services Committee went harder at Dimon, asking him repeatedly to defend the size of JPMorgan, the nation's largest U.S. bank by assets.

"Many of the American taxpayers are concerned when big banks go bad, they're left holding the loss," said Republican Representative Sean Duffy, a favorite of the conservative, small-government Tea Party movement.

Dimon said taxpayers should absolutely never have to foot the bill for a failing firm and that big banks should not be bailed out.

"No, we're not too big to fail," said Dimon, who at times appeared more tired and exasperated than during last week's hearing. "I don't think there's any chance we're going to fail," he added.

(Reporting by Sarah N. Lynch, Dave Clarke and David Henry; Writing by Karey Wutkowski; Editing by Tim Dobbyn)

• A Permanent Economic Emergency