WASHINGTON – The Securities and Exchange Commission adopted new rules Thursday requiring firms selling securities backed by mortgages, student loans and credit cards to thoroughly review the loans and report the findings to the public.

The markets for securities backed by bundles of such loans have remained weak since the financial crisis, largely because investors are unsure about the quality of the loans.

The new rules are part of the financial overhaul law enacted last summer. They will apply to offerings of asset-backed securities starting next Jan. 1.

The rules are intended “to restore investor confidence” in the markets for asset-backed securities, SEC Chairman Mary Schapiro said before the 3-2 vote. The two Republican SEC commissioners, Kathleen Casey and Troy Paredes, opposed the rules.

When the housing bubble burst in 2007 and defaults on home mortgages began to soar, securities tied to high-risk subprime mortgages became toxic. Investors in them, such as big Wall Street banks, lost billions.

The distress spread to the markets for other types of securities as investors lost confidence in their value. Banks were unable to continue selling the securities to raise cash, and the pipeline for credit froze.