Credit rating agencies failed properly to manage conflicts of interest in assigning top ratings to bonds backed by subprime mortgages and other assets, the Securities and Exchange Commission has concluded.

The rating agencies, which are paid by the issuers whose securities they rate, have come under criticism for failing to act quickly enough to warn investors about the risks of investing in complex “structured” securities. Ratings analysts are often managed by the same people who run the business side of such firms.