The Securities and Exchange Commission (SEC) on Wednesday adopted new rules to reduce the risk of runs on money funds, mainly through floating net asset value instead of a fixed share price of one U.S. dollar.

The measure was approved by the SEC in a 3-2 vote, ending a long debate between regulators and industry on how to address structural vulnerabilities in the funds dating back to the financial crisis.

"Today's reforms fundamentally change the way that money market funds operate. They will reduce the risk of runs in money market funds and provide important new tools that will help further protect investors and the financial system," said SEC Chair Mary Jo White.

Under the new rules, institutional prime money market funds are required to abandon their fix one-dollar share price and value their portfolio securities using market-based factors, the SEC said.

The rules also allow non-government money market fund to impose a fee to redeem shares and set redemption gates in order to discourage investors from withdrawing their money in times of crisis.

The reform was triggered by the crisis of money market funds, a major supply of short-term funding for corporations, after the bankruptcy of Lehman Brothers in 2008, forcing the Federal Reserve to bailout the industry.

The final rules provide a two-year transition period to enable both funds and investors time to fully adjust their systems, operations and investing practices, said the SEC.