UPDATE 3-Biden's US FTC chair to resign commission in coming weeks, memo says

Adds detail on Khan and composition of FTC commissioners

By Jody Godoy

WASHINGTON, Jan 20 (Reuters) - Lina Khan, who until Monday was an aggressive enforcer of antitrust law as the head of the U.S. Federal Trade Commission (FTC) under former President Joe Biden, will resign from the commission in the coming weeks, she told staff in a memo.

Khan challenged numerous mergers during her tenure, while working to ensure consumers and workers were not disadvantaged by powerful corporations.

Under Biden, Khan's FTC sued Amazon AMZN.O, opened an investigation into Microsoft MSFT.O, and won court rulings that blocked Kroger's KR.N $25-billion acquisition of rival grocery chain Albertsons ACI.N and the $8.5 billion merger of handbag makers Tapestry TPR.N and Capri CPRI.N.

The youngest person to lead the U.S. consumer protection and antitrust agency, Khan gained attention in 2017 when she wrote a paper arguing that Amazon had amassed monopoly power by undercutting competitor prices and harvesting consumer data.

Tech companies like Amazon had largely gotten a pass under a legal consensus starting in the 1970s that anti-competitive practices were only unlawful when they lead to higher prices for consumers, Khan wrote at the time.

Antitrust enforcers subsequently launched a crackdown on Big Tech companies, suing Google GOOGL.O and Facebook, now Meta Platforms META.O, during the first Trump administration.

Republican Commissioner Andrew Ferguson became the agency's chair on Monday when Trump took office. Khan's departure will put the FTC at a temporary stalemate, with two Republican and two Democratic commissioners.

But Republicans will have a majority on the FTC once the U.S. Senate approves Mark Meador, Trump's nominee to complete the five-member commission. A former FTC and Department of Justice attorney, Meador is viewed as pro-enforcement pick.

Some of Khan's agenda proved divisive.

A court struck down a broad ban on worker noncompete agreements aimed at allowing employees to launch competing businesses and spurring employers to compete harder for labor.

A rule that would require subscription services to offer simple cancellation methods also faces court challenges.

Ferguson and Melissa Holyoak, the other Republican on the commission, had voted against those rules as well as a recent case against an alcohol distributor that revived a long-dormant price discrimination law.

A source told Reuters on Monday that Khan plans to use her remaining time as a commissioner to complete document retention and records management as required by law, as well as other administrative tasks.

(Reporting by David Shepardson; Writing by Chris Sanders; Editing by Rod Nickel, David Gregorio and Anna Driver)

((David.Shepardson@thomsonreuters.com; 2028988324;))