The U.S. Securities and Exchange Commission's potentialsuspension of Standard & Poor's from gradingcommercial-mortgage backed bonds would threaten a practiceregulators have blamed for fueling the credit crisis.

The SEC has been investigating whether the firm bent ratingscriteria to win business in 2011, according to a person withknowledge of the matter, who asked not to be named becausediscussions between the agency and S&P about a possiblesuspension are private. In a practice known as ratings shopping,banks often seek assessments from several credit graders and choosethe ones that give the most favorable views when assemblingasset-backed bond deals linked to everything from auto loans tomortgages.

“Even temporarily taking away a slice of S&P's businesswould send a powerful message to the rest of the market that theSEC is serious about attempting to address ratings shopping,” saidJeffrey Manns, an associate professor of law at George WashingtonUniversity in Washington.