Attorney General Eric T. Schneiderman of New York sued three major banks on Friday, accusing them of fraud in their use of an electronic mortgage database that he said resulted in deceptive and illegal practices, including false documents in foreclosure proceedings.

Mr. Schneiderman, co-chairman of a new mortgage crisis unit under President Obama, filed a lawsuit against Bank of America, Wells Fargo and JPMorgan Chase in New York State Supreme Court in Brooklyn.

The database, called the Mortgage Electronic Registration System or MERS, was created in the mid-1990s for tracking mortgage ownership. It is a collaboration of top mortgage servicers, mortgage insurers and Fannie Mae and Freddie Mac, the government entities that hold many of the country’s mortgages.

“The mortgage industry created MERS to allow financial institutions to evade county recording fees, avoid the need to publicly record mortgage transfers and facilitate the rapid sale and securitization of mortgages en masse,” Mr. Schneiderman said.