Dec. 2 (Bloomberg) -- Morningstar Inc., the Chicago-based provider of investment research, began publishing credit ratings on its Web site for the 100 largest U.S. companies.

The rankings will expand over the next year to include as many as 1,000 companies currently covered by the firm’s equity analyst team, according to a statement distributed today by PR Newswire. The data will be available free of charge at Morningstar.com.

“Credit ratings are a natural extension of the equity research we’ve been producing for the past decade,” Catherine Odelbo, president of equity research, said in the statement.

The expansion into credit ratings puts Morningstar in direct competition with the three largest firms that provide rankings, Standard & Poor’s, which is owned by McGraw-Hill Corp., Moody’s Corp. and Fitch Ratings.

The companies have come under criticism by investors and lawmakers including Senate Banking Committee Chairman Christopher Dodd, who has said they wrongly assigned top credit rankings to U.S. subprime-mortgage bonds just before that market collapsed in 2007. Defaults on the debt ignited a credit crisis that has led to more than $1.7 trillion in writedowns and losses since the start of 2007.

Morningstar climbed 90 cents, or 1.9 percent, to $47.92 at 2:44 p.m. New York time in Nasdaq Stock Market composite trading.

The company said it would make forecasts and scores underlying the credit ratings available to its institutional clients. The rating scale will be similar to the letter system used by S&P and Fitch, with AAA representing the lowest risk and D indicating that a company is in default, according to the statement.

Morningstar issued ratings on companies including Exxon Mobile Corp., which was assigned a top AAA rating, Union Pacific Corp., ranked BBB for moderate default risk, and Royal Caribbean Cruises Ltd., rated B-, or high default risk.

To contact the reporter on this story: Christine Richard in New York at crichard5@bloomberg.net

Last Updated: December 2, 2009 14:53 EST