B ritain’s competition watchdog is investigating whether Amazon is harming competition and hurting consumers by giving an unfair advantage to merchants that pay for extra services. The Competition and Markets Authority’s formal investigation said yesterday that it will look into concerns that the ecommerce giant is abusing its dominance to undermine rivals, echoing similar investigations carried out by the European Union’s executive Commission and Germany’s antitrust agency. Amazon said it will work closely with the CMA during the investigation. “We believe we’ve always worked hard to help small businesses selling on Amazon to succeed, which is in both their and…