The market-regulating SEC Wednesday voted unanimously to crack down on earnings reports that depart from nationally recognized Generally Accepted Accounting Principles, or GAAP.

Under the new rule, companies may not report so-called pro forma results to the Securities and Exchange Commission or in other announcements, such as press releases, without saying how they differ from results under GAAP.

"The ability of companies to hide the ball in key financial areas will now be limited," SEC Commissioner Harvey Goldschmid said at the SEC's open meeting on the rule.

Traditionally, pro forma results were used by companies to help investors compare profits to previous years after a major merger or acquisition. In recent years, however, many companies, especially unprofitable technology companies, started touting pro forma figures that stripped out a number of expenses, such as restructuring charges and merger costs. The practice has come under scrutiny because pro forma earnings almost always make profits look rosier.

The new rule provides some exceptions for non-U.S. companies.

The five-member SEC also voted unanimously to ban stock sales by corporate insiders during pension fund "blackout" periods that last more than three business days.

The rule stemmed from allegations that top executives at now-bankrupt Enron unloaded thousands of shares of the company's falling stock during a blackout period when Enron employees could not sell.

The SEC was later scheduled to vote on other rules implementing the sweeping Sarbanes-Oxley Act, passed last July amid corporate scandals that included former energy trader Enron Corp. and telecommunications group WorldCom Inc.

These proposals include requiring companies to reveal the accounting expertise of audit committees.

Wednesday's meeting and one scheduled for next week could be "the busiest two weeks of rule-making in this agency's history," departing SEC Chairman Harvey Pitt said at the meeting.

Congress set a deadline of Jan. 26 for implementing many of the major reforms in the Sarbanes-Oxley law.

President Bush in December announced his intention to nominate Wall Street banker William Donaldson as his new SEC chairman.