More than 400 subprime-related lawsuits have been filed since last year, and half of this year's activity is concentrated in two states, according to a new report -- which referred to the current level of litigation as a "tsunami."

There were 170 subprime-related lawsuits filed in federal courts during the first quarter, Navigant Consulting Inc. reported Wednesday.

Compared to the previous "busiest quarter," first-quarter cases were 85 percent higher, the report indicated.

"The total filings are close to surpassing the savings-and-loan crisis litigation of the early 1990s," the litigation consulting firm stated.

The rising caseload reportedly began in 2007, with 181 of last year's 278 cases being filed during the second half of the year.

Borrower class actions accounted for 46 percent of cases filed -- though class actions were involved in 76 percent of all first quarter cases, Navigant reported. Securities represented just over a quarter of the litigation, while commercial contract disputes made up 10 percent of filings.

A report announced earlier this month by RiskMetrics Group indicated that the targets of at least 67 subprime-related securities class actions filed this year were underwriting firms, investment managers, home builders and mortgage lenders.

A first-quarter analysis of 42 lawsuits and other legal actions reported by MortgageDaily.com indicated mortgage litigation was dominated by cases related to foreclosures, investors and secondary marketing.

Some atypical subprime-related plaintiffs emerged such as the municipalities of Baltimore and Cleveland, Navigant said in its first-quarter report. Half of the 170 first-quarter cases were filed in either California or New York.

Of the 448 federal lawsuits filed from January 2007 through March 2008, 86 percent were still active at the end of March, Navigant noted.

"What we saw in 2007 was a mild breaking wave compared to the tsunami we are witnessing now," Navigant Managing Director Jeff Nielsen said in the statement. "Like the S&L cases, this is a process that will likely take years to play out."