Online retailing giant Amazon was criticized as "anti-competitive" Saturday for its latest promotion that encourages consumers to enter stores and leave empty-handed, after reporting back the prices they find there.

The deal dubbed "Price Check" involves customers finding and sharing in-store prices and receiving a discount of five percent -- to a maximum of $5 -- from the online retailer for that item if Amazon has it in stock.

The move was sharply criticised by Maine Senator Olympia Snowe, a member of the Senate Committee on Small Business and Entrepreneurship, who called the move a direct assault on retail stores.

"Amazon's promotion -- paying consumers to visit small businesses and leave empty-handed -- is an attack on Main Street businesses that employ workers in our communities," she said in a statement this week.

The deal, accessed through a new smartphone application from the Amazon website, can be applied three times for a total savings of $15 on electronics, sporting goods, music, DVDs and other items.

The Retail Industry Leaders Association (RILA) also criticized the promotion, saying that "central to this tactic is Amazon's continued practice of using a pre-Internet loophole to avoid state sales tax collection."

The group called on lawmakers to rein in what it called the company's "exploitative" practises.

The online retailer is regularly targeted by trader associations who believe the company gains an unfair competitive advantage due to being exempt from VAT taxes in most US states.