U.S. technology giants are headed for their biggest antitrust showdown with Congress in 20 years as lawmakers and regulators demand to know whether companies like Alphabet Inc.’s Google and Facebook Inc. use their dominance to squelch innovation.

Executives from Google, Facebook, Apple Inc. and Amazon.com Inc. are set to appear Tuesday before the House antitrust panel, whose Democratic chairman is leading an investigation into the market power of the biggest tech companies and their effect on competition.

The hearing harkens back to Microsoft Corp. co-founder Bill Gates’ appearance before the Senate in 1998 when Microsoft was the target of government scrutiny into its monopoly in computer operating systems. Two months later, the Justice Department filed a landmark antitrust lawsuit against Microsoft that reined in its practices and nearly led to the company’s breakup.

“This is really a deep dive by the committee to understand what’s going on in the tech sector, what needs to be done in terms of antitrust enforcement but also to understand better whether there is a need for change in the law,” said Gene Kimmelman, a senior adviser at the policy group Public Knowledge, who served in the Justice Department’s antitrust division under President Barack Obama.

While the executives testifying Tuesday don’t have the star power of Gates, their appearance marks the first time the largest technology companies will face questions from lawmakers amid a rising chorus of criticism that they are violating antitrust laws. That was the same accusation leveled at Microsoft two decades ago.

Rhode Island Democrat David Cicilline, who leads the antitrust panel, is bearing down on technology companies as antitrust enforcers prepare their own scrutiny of the industry. The Justice Department and the Federal Trade Commission, which share antitrust jurisdiction, have taken the first steps toward investigating conduct by the biggest companies, with the Justice Department taking responsibility for Google and Apple, and FTC overseeing Facebook and Amazon.

Tuesday’s hearing will focus on innovation and entrepreneurship. One of the key complaints from critics of the big tech companies is that they can use their power to thwart competition from smaller rivals. Academic research has shown a steady decline in business start-ups across the economy. One possible explanation is that rising market concentration across industries effectively shuts out entry by new businesses.

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