New York is suing Credit Suisse Securities and affiliates, claiming they misled investors about the care taken in evaluating their residential mortgage-backed securities.
The suit filed Tuesday in Manhattan under New York's Martin Act alleges Credit Suisse deceived investors before the 2008 market collapse.
Attorney General Eric Schneiderman says the securities sponsored and underwritten by Credit Suisse in 2006 and 2007 have lost about $11.2 billion.
Zurich-based Credit Suisse says Schneiderman "recycles baseless claims" from private lawsuits.
Schneiderman is co-chair of a task force established by President Barack Obama to investigate misconduct in the pooling and sales of those securities.
Last month, he filed a similar lawsuit against JPMorgan Chase & Co., alleging fraud by Bear Stearns before its 2008 collapse and subsequent sale to the New York bank.