FILE PHOTO: Amazon CEO Jeff Bezos discusses his company's new Fire smartphone at a news conference in Seattle, Washington June 18, 2014. REUTERS/Jason Redmond

WASHINGTON (Reuters) - Two U.S. senators asked Amazon.com Inc Chief Executive Jeff Bezos on Monday how the “Amazon’s Choice” badge on certain products is determined and whether the mark deceives consumers into purchasing “products of inferior quality.”

“We are concerned the badge is assigned in an arbitrary manner, or worse, based on fraudulent product reviews,” Democratic Senators Bob Menendez and Richard Blumenthal said in the letter to Bezos.

The “Amazon’s Choice” mark is a small badge that appears next to certain items, similar to its “Best Seller” mark.

Amazon sued in 2015 to block companies that were writing fake reviews and then selling them to retailers on the site looking to boost their products’ sales.

The senators said the lack of information on how Amazon determines which products receive the badge has led them to question whether Amazon is using it to “promote its own products over competitors’ products, potentially disadvantaging smaller sellers on the platform.”

Amazon did not immediately respond to a request for comment.

The senators requested a “detailed explanation of the process” that Amazon uses to determine which products are deemed as Amazon’s Choice and if the retailer uses an algorithm to do so. They also asked if Amazon employees personally review the products to “ensure they meet a certain quality threshold.”

Amazon has been criticized for its power over third-party sellers on its site, who must pay for advertising to compete against first-party and private-label sales by Amazon’s own brands.

The U.S. Department of Justice announced in July that it was investigating whether big technology companies, including “some retail services online” were engaging in anticompetitive practices.