The SEC has adopted new rules aimed at increasing transparency and accountability at credit rating agencies, after criticism that the agencies contributed to the financial crisis by giving top ratings to mortgage-backed securities that later collapsed.

The SEC approved a series of rules, including ones that force ratings agencies to crack down on conflicts of interest.

According to The Wall Street Journal, the SEC voted to prohibit a firm from rating a security if the firm or an affiliate helped structure it, to forbid employees who work on ratings from taking part in fee discussions or arrangements, and to ban them from accepting more than $25 in gifts from security issuers, underwriters or sponsors.

The SEC said its actions followed a 10-month examination of three major credit rating agencies, finding significant weaknesses in ratings practices.

"These comprehensive rules touch every aspect of the credit rating process " from conflicts of interest, to publication of ratings methodologies, to disclosure of ratings track records," SEC Chairman Christopher Cox said in a statement .

"The SEC's examinations of credit rating agencies uncovered serious deficiencies that these rules will address, so that investors and markets will have better information to guide investment decisions."

The SEC also approved new rules requiring credit rating firms to provide annual reports that detail all upgrades and downgrades for each asset class for which it provides credit ratings.