Timothy J. Muris, who spearheaded creation of a do-not-call list used by millions of people to block unwanted telemarketing, said yesterday he was stepping down as chairman of the Federal Trade Commission.

To replace him, the White House announced last night that President Bush was nominating Deborah P. Majoras, a Washington antitrust attorney who recently left the Justice Department to return to private practice. If confirmed by the Senate, Majoras would fill out Muris's term, which expires in 2008.

Majoras is best known for helping to craft the federal government's settlement of its years-long case against Microsoft Corp. during a nearly three-year stint at the Justice Department's antitrust division. She left the Justice Department at the end of last year to return to the firm of Jones Day. Citing upcoming confirmation hearings, she declined to comment last night.

Muris, 54, said he is leaving in part because he accomplished most of what he set out to achieve.

"I'm extremely proud of how we advanced the anti-fraud agenda," he said. "We've gotten more money back for consumers than ever, pursuing cross-border cases, working more with criminal authorities."

Muris will step down this summer and return to George Mason University's School of Law, where he will head a committee to search for a new dean.

The timing of his departure will give Congress an opportunity to consider Majoras's nomination before the fall elections are held and a new Congress is seated.

Muris's primary legacy will be his aggressive campaign to create a national do-not-call list, fighting the telemarketing industry and major corporations that sell their goods and services over the phone.

Nearly 60 million telephone lines have been registered. The list went into effect in October, when a federal appeals court gave the go-ahead, saying a lower court's ruling that the list was an unconstitutional restriction on telemarketers' free speech was likely to be overturned, which it was about four months later.

Following a course set by the previous chairman, Robert Pitofsky, a Democrat, Muris also attacked products that promised easy, no-pain weight loss and credit-counseling firms that used deceptive business practices.

That surprised many who had expected Muris, a Republican who as a key FTC official in the Reagan administration spoke out for limited government oversight, to lead the agency with a more hands-off approach to industry.

Fellow Commissioner Mozelle W. Thompson, a Democrat who has had his differences with Muris, said, "He's done a very good job here at having a consumer focus, paying attention to such important initiatives as the do-not-call list. "

Muris's moves stood out in the Bush administration, which consumer advocates consider one of the most pro-business in years.

"Muris ran a lot of forums that were open," said Mark Cooper, research director for the Consumer Federation of America. "He gave people the sense that he was listening. And he genuinely believes in competition. He doesn't favor big guys, necessarily."

Iowa Attorney General Tom Miller, a Democrat, said Muris often worked cooperatively with states, especially in going after predatory lenders.

Under Muris, the FTC also produced an exhaustive and critical assessment of the U.S. patent system, urging several reforms.

One controversial section questioned whether too many patents were being issued, especially in the areas of software and online business methods, such as Amazon.com's "one-click" shopping system.

In her tenure at the Justice Department's antitrust division, Majoras, a graduate of the University of Virginia law school, was a popular deputy with colleagues and was known for logging exceptionally long hours.

But the Microsoft settlement was controversial in the legal and academic communities.

The settlement imposed restrictions on the company's conduct that are still being monitored by the Justice Department. But it was denounced as being a slap on the wrist by company rivals, consumer groups, many antitrust scholars and several states, which sought tougher sanctions.

A federal court judge rejected that challenge last summer, causing most of the challenging states to end their efforts. But Massachusetts took the case to the U.S. Court of Appeals for the D.C. Circuit, which has yet to issue a ruling.

Majoras argued the case for the Justice Department.

Miller of Iowa, one of the original challenging states, said he respected Majoras and their differences over how best to deal with Microsoft, which was found by courts to have abused its monopoly in the market for computer operating systems.

But he said many state attorneys general were unhappy with the Justice Department's position that the states should have little role in antitrust enforcement in cases in which they disagree with the federal government's approach.

"That raises some concerns" about how she would approach the FTC's antitrust authority, Miller said. "Our approach is to wait and see."