Britain’s competition regulator started a formal investigation on Friday into whether Amazon and Google may not have done enough to prevent or remove fake reviews. Along with regulators in the United States and the European Union, the Competition and Markets Authority (CMA) has stepped up its scrutiny of big tech firms in recent years. The British regulator said it will gather more information to decide if the firms may have broken consumer law by taking insufficient action to protect shoppers. Both Google and Amazon said they were continuing to assist the CMA. CMA action last year over the trading of fake reviews resulted in Facebook, Instagram, and eBay removing groups and banning individuals for buying and selling fake reviews on their sites. Google said on Thursday it would delay blocking tracking cookies on its Chrome browser following intervention by the CMA. The CMA started its investigation into reviews in May …