A bipartisan group of House lawmakers is demanding that Amazon prove itself by providing evidence to counter claims in news reports about its own brand’s special treatment over products from other sellers.

In a letter sent Monday to Andy Jazzy, Amazon’s current CEO, five members of a congressional committee accused Jeff Bezos, Amazon’s former CEO and founder, and other company executives of misleading lawmakers.

Citing recent research by Reuters, The Markup and others on how Amazon uses third-party sellers to copy products and, in some cases, give its own ads more prominence, lawmakers are asking questions about how Amazon treats its own trademarks compared with those of other companies that offer products on its platform.

In response to the reports, Amazon called them “incorrect and unsubstantiated” stressing further that its employees are strictly prohibited “from using non-public, seller-specific data to determine which store brand products to launch,” and that its search results were designed “to feature the items customers will want to purchase, regardless of whether they are offered by Amazon” or by another seller.