Seeking to show victories against the kind of ground-level fraud that contributed to the housing crash, federal authorities said Thursday that they had filed criminal charges in recent months against 1,200 mortgage brokers and others accused of cheating banks and borrowers of $2.3 billion.

White-collar crime experts said the size and scope of what the government presented Thursday — dubbed Operation Stolen Dreams — represented an unprecedented crackdown on mortgage fraud.

The cases, including criminal charges against more than 30 defendants in Southern California, were announced at news conferences in Washington, New York, Ventura and elsewhere.

They were coordinated by the Obama administration’s Financial Fraud Enforcement Task Force, a recent collaboration among a host of federal and state agencies including the FBI, the Department of Housing and Urban Development and state attorneys general.

“We know that mortgage fraud ruins lives, destroys families and devastates whole communities, so attacking the problem from every possible angle is vital,” Atty. Gen. Eric Holder said in Washington. “These schemes are despicable, they are dangerous to our economy, and they will not be tolerated.”

The numbers reflect a steady increase in the last seven years in the number of open FBI mortgage-fraud cases, to more than 3,000 in May from fewer than 500 in 2003.

The charges filed by federal prosecutors in Los Angeles, Orange and Riverside counties included two cases in Ventura County with a total of 14 defendants, said Andre Birotte, the U.S. attorney based in Los Angeles.

The Ventura County defendants are accused of filing fraudulent loan applications, collecting millions of dollars in fees and commissions, and causing millions of dollars in losses when the homes went into foreclosure, Birotte said in Ventura.

The announcements, coupled with the arrest Tuesday of the former chairman of a large Florida mortgage company on charges of engineering a $1.9-billion fraud, illustrate the two levels of misconduct the government is going after.

Cases like those publicized Thursday are relatively easy to investigate and prosecute, former federal prosecutor John Hueston said. But not always that easy: Separate civil charges were announced against 395 people and companies, suggesting to Hueston that the government had decided not to bring criminal charges in those cases.

Holder said $147 million had been recovered in the civil cases, an amount Hueston said was not that big given the magnitude of the abuses.

Nonetheless, Hueston said, the large number of cases unveiled Thursday would send a serious message with a real deterrent value.

The government seemed to stretch to include every case it could in the tally. Of the criminal defendants listed, 336 already have been convicted and 206 have been sentenced.

In one of the New York cases, a tax preparer is accused of selling fake pay stubs and tax documents to mortgage and real estate brokers, who allegedly used the documents to apply for loans. Authorities said 17 people were indicted as a result of that investigation.

In another New York case, prosecutors allege that a company offered to help struggling homeowners around the country but did nothing once the borrowers paid the firm’s upfront fees.

“Preying on hundreds of struggling homeowners who were desperate for any kind of relief, the defendants stole from those who could afford it least,” said Neil Barofsky, the special inspector general for the Treasury Department’s Troubled Asset Relief Program.

Of the cases unveiled nationwide, some relate to conduct during the housing boom, while others deal with behavior after the meltdown.

“Some of these folks have engaged in one kind of mortgage fraud in one financial environment and a different kind of mortgage fraud in another financial environment,” said Preet Bharara, the U.S. attorney for Manhattan.

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