(Bloomberg) -- The US Federal Trade Commission’s antitrust case against Amazon.com Inc. relies on anecdotal evidence from a handful of online merchants and fails to prove that the online retailer’s practices hurt consumers, the Seattle company’s lawyers argued Friday in a motion to dismiss the complaint.

The motion challenges a key assertion made by the agency that Amazon causes prices to go up on competing websites. Online brands and merchants have testified that they don’t offer lower prices on other sites because Amazon, which captures more than one-third of online spending in the US, will punish them by making their products less visible on Amazon.

“The Complaint does not identify a single product or product category for which prices have risen as a result of the challenged conduct,” Amazon attorney Heidi Hubbard wrote in the motion. “Instead, it implausibly, and illogically, assumes that Amazon’s efforts to keep featured prices low on Amazon somehow raised consumer prices across the whole economy.”

The FTC sued Amazon in September accusing the e-commerce giant of monopolizing online marketplace services by degrading quality for shoppers and overcharging sellers, part of a broader agency challenge of the power of big technology companies.

The case is FTC v. Amazon, 23-cv-1495, US District Court, Western District of Washington (Seattle).

--With assistance from Leah Nylen.

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