Washington ? Leaders of three big telecom companies engulfed in accounting scandals faced Senate criticism Tuesday over the excesses of executives who cashed out millions in company stock, while the nation’s biggest brokerage denied it knowingly and helped Enron hide its true financial condition.

At the White House, President Bush signed into law the most far-reaching government crackdown on business fraud in 70 years, hoping to restore investor confidence with a promise of “hard time” for corporate wrongdoers.

President Bush greets FBI Director Robert Mueller, center, and Securities and Exchange Commission Chairman Harvey Pitt, right, after signing a strict new law on corporate responsibility. The law, signed Tuesday, substantially changes business accounting practices and imposes penalties for violators.

“This law says to every dishonest corporate leader, ‘You’ll be exposed and punished.’ The era of low standards and false profits is over,” Bush declared at a signing ceremony marked by considerable fanfare and the absence of corporate executives.

An election-year wave of accounting scandals, which drove down the stock market and threatened political damage to the White House and Republican lawmakers, helped propel the bill through Congress with extraordinary speed.

On Capitol Hill, skeptical senators accused Merrill Lynch & Co. of abandoning its moral, if not legal, responsibility to investors by helping Enron hide its financial problems.

“Merrill Lynch was fully aware of what Enron was trying to do,” said Sen. Carl Levin, D-Mich., chairman of the investigative subcommittee of the Senate Governmental Affairs Committee.

At a separate hearing with the leaders of WorldCom Inc., Global Crossing Ltd. and Qwest Communications International Inc., Sen. John McCain, R-Ariz., noted the millions in stock options given to leaders of telecom companies who cashed them in before the firms collapsed. The options were supposed to be tied to performance.

“Why didn’t you immediately ask for that money back?” McCain asked them at the Senate Commerce Committee hearing.

The officials responded that until allegations against the former executives are proven valid, the companies cannot move against them.