Popular phone accessory maker PopSockets accused Amazon of "strong-arming" it and failing to remove fake products.

David Barnett, CEO of PopSockets, testified during a House Judiciary antitrust subcommittee hearing on competition in the digital economy in Colorado on Friday.

Barnett said Amazon pressured PopSockets to lower the price of its products on the platform and said if it failed to do so, the company would source product from the "gray market," or third-party sellers. PopSockets sells grips that attach to the back of cellphones.

"One of the strangest relationships I've had with a retailer is with Amazon," Barnett said. "The agreement appears to be negotiated in good faith, but what happens is there are phone calls where we get bullying with a smile."

An Amazon spokesperson told CNBC in a statement that the company sought to continue working with PopSockets to provide "competitive prices, availability, broad selection and fast delivery" for those products to its customers.

"Like any brand, however, PopSockets is free to choose which retailers it supplies and chose to stop selling directly through Amazon," the spokesperson said. "Even so, we've continued to work with PopSockets to address our shared concerns about counterfeit, and continue to have a relationship with PopSockets through Merch by Amazon, which enables other sellers to create customized PopSockets for sale."

Barnett said Amazon uses a variety of tactics to "bully" businesses, such as threatening to send excess inventory back at a cost to the company. He also disputed Amazon's argument that there are other online marketplaces for businesses to sell their goods.