"Investors thought they were getting objective information but they got misled and our entire economy paid a heavy price," Cooper said. "These misrepresentations played a major role in creating the national financial crisis, and they must be prevented from happening again."
The suit - filed in Wake County Superior Court - comes a day after the federal government filed a complaint against Standard & Poor's, accusing the company of fraud for giving high ratings to risky mortgage bonds that helped bring about the financial crisis.
Cooper is joined by attorneys general in Arizona, Arkansas, California, Colorado, Delaware, the District of Columbia, Idaho, Iowa, Maine, Missouri, Pennsylvania, Tennessee, and Washington. Connecticut, Illinois and Mississippi previously filed actions against S&P.
The federal lawsuit filed Monday is the first enforcement action the federal government has taken against a major rating agency related to the financial crisis.
S&P, a unit of New York-based McGraw-Hill Cos., has denied wrongdoing in that case.