Amazon.com Inc.’s takeover of Metro-Goldwyn-Mayer is sparking fresh criticism about the spreading tentacles of America’s technology giants, but the deal underscores how competition watchdogs have their hands tied when it comes to curbing the companies’ growth.

Critics of tech firms in Washington on Wednesday slammed the MGM deal as the latest example of how the industry’s biggest players snap up companies to expand their reach, even as they face a flurry of antitrust lawsuits and moves by lawmakers to rein them in.

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“In acquiring MGM Studios, Amazon is brazenly trying to take over another sector of the economy,” said Sarah Miller, the executive director of the American Economic Liberties Project, an anti-monopoly organization in Washington. “Congress should respond quickly by passing bipartisan legislation to ban mergers by large tech firms.”