A prominent Republican senator on Thursday urged U.S. competition regulators to reopen an investigation into Google and its practices in online search and digital advertising.

Google not only enjoys a “dominant position” in the search marketplace, said Sen. Orrin G. Hatch (Utah), but the tech company has expanded its reach since 2013, when the Federal Trade Commission closed a probe into Google without launching a major enforcement action.

In a letter to the FTC, Hatch — a member of the Senate Judiciary Committee and its antitrust subcommittee — asked the agency to “consider the competitive effects of Google's conduct” in light of what he said were “disquieting” reports of potentially harmful behavior by the search giant.

The letter raises the stakes of a difficult week for Google, which came under fire from President Trump on Tuesday when he tweeted allegations that the company is biased against conservative media and hinted that his administration could take action against the company. Google has denied the accusations. It did not immediately respond to a request for comment Thursday.

Hatch's letter does not openly reiterate Trump's charges. But it cites unnamed reports claiming that “Google has, on occasion, decided to remove from its platforms legal businesses that the company apparently does not agree with.” Asked for specifics, Matt Whitlock, a spokesman for Hatch, pointed to decisions Google has made to ban listings of firearms equipment on Google Shopping — a move covered by Search Engine Land — as well as advertisements for payday loans, which were reported by The Washington Post, the New York Times and others.

Hatch also cited a "60 Minutes” segment covering Google's size and role in the Internet ecosystem.

More broadly, Hatch said, Google's practice of collecting data on consumers across its Android operating system and email products has raised compelling privacy concerns.

Google and Hatch tussled goodnaturedly in July, when an erroneous change to Hatch's Wikipedia page added a date of death that was then picked up by Google and amplified in its search results for the lawmaker.

The FTC said it had received Hatch's Thursday letter but declined to comment further.

In 2013, the FTC’s five commissioners found little evidence that Google manipulated its search results to favor its own properties. The agency concluded that Google’s periodic updates to its algorithms were in fact beneficial to consumers, even if they happened to disadvantage other companies. The commission voted unanimously to close the investigation, although an internal memo that inadvertently leaked two years later showed divisions about how best to proceed.

Google is also facing pressure from other lawmakers who have invited the company's chief executive, Sundar Pichai, to testify next Wednesday before the Senate Intelligence Committee. Although Google offered to send its general counsel, Kent Walker, the company has declined to make Pichai available, prompting the committee to request that co-founder Larry Page appear. Sen. Mark R. Warner (D-Va.) said Wednesday on CNBC that the hearing examining the practices of Facebook, Twitter and Google may proceed with “an empty chair” if Google does not send a “senior decisionmaker."

Thursday's letter strikes a starkly different tone from a speech Hatch gave just over a year ago, when he cited Google to back up an argument against heavy-handed antitrust enforcement.

"Across the Atlantic, our friends in the European Union have levied a massive fine against Google for anticompetitive conduct,” Hatch said at the time. While he declined to opine on the merits of the European Union's fine, Hatch said it was imperative that the United States consider the consumer benefits of Google's behavior.

"The ultimate inquiry should be whether consumers are better off as a result of Google’s actions,” he said.

Hatch now appears to have concluded in the negative.