The New York attorney general, Eric T. Schneiderman, sued the Credit Suisse Group on Tuesday, accusing it of misleading investors in mortgage-backed securities.

The lawsuit claims that Credit Suisse, Switzerland’s second-largest bank after UBS, misrepresented the quality of loans underlying residential mortgage-backed securities it sponsored and underwrote in 2006 and 2007, costing investors $11.2 billion.

The bank, which is based in Zurich, did not adequately evaluate the loans and ignored the defects its limited review uncovered, the lawsuit said. The suit, filed in New York State Supreme Court, also said the bank did not perform promised due diligence. The lawsuit was brought under the Martin Act, a New York securities fraud statute.

Credit Suisse said it rejected the complaint and looked forward to presenting its defense in court. The complaint "recycles baseless claims from private lawsuits and uses an inaccurate and exaggerated number," the bank said in a statement, apparently referring to the $11.2 billion loss figure. The bank announced a management shake-up on Tuesday.