An app developer is accusing Apple of having manipulated app rankings in its App Store in new court filings.

The app developer said it realized that its app had suddenly jumped in Apple's rankings following a report from The New York Times about the tech giant's apps being ranked highly in its own store.

The court filings have appeared as lawmakers are increasingly scrutinizing whether large tech firms are engaging in anticompetitive behavior.

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An email app developer is accusing Apple of having manipulated App Store rankings, once again raising concerns about the influence large tech firms hold over the digital platforms and marketplaces they operate.

The company, Blix, says in new court filings that it had discovered evidence showing that Apple had altered the rankings of apps in its App Store, The Washington Post first reported.

The founders of Blix, which offers an email-management app called BlueMail, said they noticed a change to the way Apple ranks apps around the end of September. BlueMail had moved from 143rd all the way up to 13th place in the company's rankings for mail apps.

The change occurred after The New York Times published a report about how Apple's apps had historically been ranked first in App Store search results. The email app provider used data from SensorTower to examine the changes in rankings over time.

"On information and belief, Apple changed its search algorithms in an apparent attempt to remove the techniques for manipulation and suppression that it had previously employed and that were now under scrutiny in the wake of the New York Times extensive report," the app creators say in the document.

Blix is also accusing Apple of patent infringement and antitrust violations.

Apple did not immediately respond to Business Insider's request for comment.

Blix's accusation comes as tech giants such as Apple, Amazon, Facebook, and Google are under more scrutiny than ever over whether they're engaging in anticompetitive business practices. The Department of Justice said in July that it was launching a broad probe into market-leading platforms for search, social media, and e-commerce to determine whether they were harming competition.

Representatives from Apple, Google, Amazon, and Facebook also appeared in July before a House subcommittee, which grilled the firms on the size and influence of their businesses and how that impacted competition.

Democratic Senator Elizabeth Warren has been a particularly vocal critic of tech industry giants. She proposed a sweeping plan back in March that called for big tech firms to be broken up, which would mean rolling back certain acquisitions, such as separating Amazon from Whole Foods and breaking Instagram away from Facebook.

Although Warren's proposed plan didn't initially mention Apple, she later told The Verge that her plan applies to it, too. "It's got to be one or the other," Warren said, referring to Apple's relationship to its App Store. "Either they run the platform or they play in the store. They don't get to do both at the same time."

Apple's App Store has been under scrutiny in recent months, especially as Apple continues to launch new apps and services that compete with third-party offerings in its store. The New York Times reported in April, for example, that Apple had removed or restricted several screen-time-management apps after it launched its own, similar feature.

Popular music streaming app Spotify also filed an antitrust complaint against the tech giant earlier this year, saying that the 30% cut Apple takes from transactions made through the App Store makes it difficult to price its offering competitively.