WASHINGTON — N.C. Attorney General Roy Cooper has filed a lawsuit against ratings agency Standard & Poor’s, joining more than a dozen of his peers in alleging that the company inflated the ratings on risky investments.

The announcement came a day after the U.S. Department of Justice saidit would bring its own suit against S&P, claiming the company caused more than $5 billion in losses by fraudulently giving high ratings to complex bundles of mortgages despite knowing the housing market was in trouble.

Cooper’s suit, filed in Wake County, alleges wrongdoing starting in 2001, becoming more common between 2004 and 2007, and lasting until 2011. The lawsuit claims S&P changed its models to give favorable ratings to products pitched by Wall Street banks that paid the company hefty fees.

The suit seeks to force the company to stop claiming that it is objective and to pay penalties.

“Investors thought they were getting objective information but they got misled and our entire economy paid a heavy price,” Cooper said in a statement. “These misrepresentations played a major role in creating the national financial crisis, and they must be prevented from happening again.”

In a Monday statement, S&P said a Justice Department suit would be “without factual or legal merit” and “unjustified.” The company said it downgraded mortgage-backed securities and “repeatedly warned of deteriorating conditions in the housing market,” which it says is evidence that the government’s claims against it are wrong.

The company said it has brought in new leadership and invested $400 million into its ratings to boost risk management and strengthen independence.

“At S&P we have taken to heart lessons learned from the financial crisis and made extensive changes that reinforce the integrity, independence and performance of our ratings, including compliance with today’s enhanced regulatory oversight,” the company said.

Cooper has joined several multistate actions in recent months, most notably a $25 billion accord with the country’s largest mortgage servicers announced last year.

Last week, Cooper announced North Carolina had joined a settlement with foreclosure service company Lender Processing Services that paid $120 million across 46 states.

Dunn: 704-358-5235 Twitter: @andrew_dunn