The number of class action lawsuits filed against Wall Street firms surged in the last year, fueled by the meltdown in the subprime mortgage market, according to new research published yesterday.

There was a 43% jump in the number of securities fraud class action lawsuits last year to 166 suits — 100 of which were filed after the mortgage crisis hit, the study by Stanford Law School and Cornerstone Research found.

“I think we’re going to see more litigation coming out of the subprime crisis,” a partner at law firm Bernstein Litowitz Berger & Grossmann, Gerald Silk, said.

The finance sector led the way for class action suits, with 47 Wall Street firms sued in 2007, more than four times the number sued in 2006. The Second Circuit, which includes New York’s federal courts, was the site of the most filings, with 58 suits.

New York City itself has gotten into the lawsuit game, with the city’s retirement and pension funds for city workers filing lawsuits against mortgage lender Countrywide Financial Corp., claiming the lender misrepresented the risk of its mortgage-backed securities.

“It’s hard to say, but with the volatility back up, I would expect the number of suits to be above what we’ve seen in the past couple of years,” the vice president of Cornerstone Research, John Gould, said.

Last January, Senator Charles Schumer and Mayor Michael Bloomberg issued a joint report calling for fewer restrictions on the financial industry, including restricting class-action lawsuits against companies by capping awards and encouraging more arbitration. They warned that if restrictions on Wall Street were not loosened, the city could lose as much as $25 billion in cash flows generated by the financial sector.

“Let’s be clear: The financial services industry is one reason that the 20th century was the American century and that New York became the world’s capital,” Mayor Bloomberg said at the time.

Mr. Bloomberg and Senator Schumer wrote an op-ed piece in the Wall Street Journal in November 2006 citing the soaring costs of securities class-action litigation saying, “It may be time to revisit the best way to reduce frivolous lawsuits without eliminating meritorious ones.”

“I think you’re going to continue to see impaired assets being written off by companies, and investors claiming that those writedowns should have been taken earlier, and that the valuations were not accurate when disclosed,” Mr. Silk said. He is representing New York-based publisher Unisystems Inc., which is suing State Street Corp. for investing its retirement funds in the risky mortgage market.

But while more class action lawsuits related to subprime mortgage losses are expected, litigation rates as measured by the number of suits filed have actually been on the wane for the past several years. Even with the surge in class action suits in the second half of 2007, for example, the number was below the 10-year annual average of 194 lawsuits.

Still, an increase in volatility in the market like the one that is now taking place as a result of the subprime mortgage problems, is directly correlated with an uptick in the number of lawsuits filed, Mr. Gould said. In fact, a 10-point increase in the S&P index that measures volatility in the market is associated with 12 additional litigations every quarter, he found.

Last year, Messrs. Schumer and Bloomberg acknowledged that securities class action lawsuits had been dropping, but pointed out, “if economic conditions were to decline in the future, then a strong resurgence of lawsuits would likely follow.”