As U.S. authorities seek to make Wall Street pay for its role in triggering the financial crisis more than four years ago, banks are starting to fight back, frustrated that they are being asked to pay more than once for the same conduct.

The result may be that federal and state authorities trying to extract penalties from the banks are forced to go through lengthy courtroom battles, instead of getting hundreds of millions of dollars through relatively quick settlements.

In the past two weeks, two of the biggest banks were hit with separate mortgage-related lawsuits.

One from the U.S. Attorney's office in Manhattan accused Wells Fargo of misleading the government in a "longstanding and reckless" pattern of certifying the quality of questionable home loans and failing to report problems on others.

It said the deception forced the government to pay out hundreds of millions of dollars in insurance claims. Authorities are seeking hundreds of millions of dollars in damages.

Instead of quickly settling the charges, as has happened in most financial-crisis cases, Wells Fargo is contesting the allegations.

Part of its defense will be that the US$25 billion federal-state mortgage settlement reached earlier this year with top banks already cleared out some of this liability, Wells Fargo Chief Financial Officer Tim Sloan said in an interview on Friday.

"There was a lot of disappointment from our perspective in terms of how it was handled, and in particular we were very disappointed in some of the sensational allegations that were made," Sloan said, adding that the bank strongly denies the charges. The earlier settlement covered a certification that Wells says is partly at issue in the new complaint.

In the other case, New York State Attorney General Eric T. Schneiderman last week filed a civil suit against JPMorgan for alleged fraud at Bear Stearns, which JPMorgan bought at the government's request in 2008.

JPMorgan is also fighting back against those charges. Chief Executive Jamie Dimon lashed out this week in Washington at a public event, saying his bank has already paid its price. It took on up to $10 billion in losses related to Bear Stearns for doing the Federal Reserve "a favor.

Rita Glavin, a former Justice Department official who is a partner at the law firm Seward & Kissel, said banks may be reaching a point where they don't see the logic in settling cases because it's not allowing them to move past the liability.

"You may be seeing them saying, we're going to draw a line in the sand, and we're not simply going to lay down and get rolled over," Glavin said.

The strategy does come with some danger of new information being disclosed that private litigants can use in their own lawsuits against the banks.

But the civil cases also indicate the banks will likely face no criminal charges for the same conduct, potentially giving the banks less reason to immediately resolve them.

"If the banks have come to the determination that the worst that is going to happen is this civil case, then there is less of a downside for going forward," said Neil Barofsky, former inspector general of the TARP bailout who now teaches at New York University School of Law.

The Justice Department declined to comment. James Freedland, a spokesman for the New York Attorney General's office, said about the JPMorgan case: "It would be the ultimate legal loophole if accountability for billions of dollars worth of fraud upon taxpayers and investors could simply disappear into the ether because ownership of a company changed hands."

Some see a pattern of fresh aggression from authorities, especially out of New York, where top enforcement officials are elected. New York state banking regulator Benjamin Lawsky, who was appointed by the governor, came under fire in August when he broke from federal investigators and threatened to yank British bank Standard Chartered's state banking license over transactions tied to Iran.

Not all expected action has panned out. Goldman Sachs faced potential action from the Securities and Exchange Commission for its role in selling certain subprime mortgage securities, after it already agreed in 2010 to $550 million to resolve SEC charges related to another subprime mortgage product. The bank disclosed in August the SEC had dropped its investigation.

Drip, drip, drip

For years, government enforcers have been criticized for not being forceful enough in pursuing marquee Wall Street banks and bankers for recklessly churning out loans, then spreading around the risk by repackaging and selling securities backed by those loans.

Earlier this year, President Barack Obama announced a new financial fraud task force. Bringing together federal and state enforcement efforts and avoid overlapping cases, it was billed as the most serious effort yet to bring high-level cases.

New York state's case against JPMorgan, for example, brought together the work of the Justice Department and investigators at the Federal Housing Finance Agency's inspector general's office.

But JPMorgan still faces potential action from the U.S. Securities and Exchange Commission, which is probing activity at JPMorgan Securities related to two mortgage securitizations.

JPMorgan disclosed that probe in February of this year, roughly eight months after JPMorgan Securities agreed to pay $153.6 million to settle charges it misled investors in a complex mortgage securities transaction.

Wells Fargo also faces potential SEC action related to the housing crisis. The bank received notice it may face SEC action related to its mortgage-backed securities offerings.

"We need to come up with some type of global settlement and say, 'The end. This is it.' It's just drip, drip, drip," said Nancy Bush, a veteran bank analyst and contributing editor with SNL Financial.

It's difficult to determine how much liability is still out there and whether banks have put enough money away to cover it.

JPMorgan and Wells Fargo both reported third-quarter results on Friday. Wells Fargo's "operating losses," an expense category that includes litigation, were $281 million in the third quarter, down nearly by half from the second quarter. The bank's reserves take into account the suit from the Manhattan U.S. Attorney's office, Sloan told analysts in a conference call.

JPMorgan reported litigation expenses of $800 million, up from $300 million in the last quarter but down from the $1.3 billion recorded one year ago.