Officials at the U.K.’s Competition and Markets Authority could launch an antitrust investigation into Facebook Inc. in the coming months, the Financial Times reported today.The probe will seek to determine whether the company uses the data it collects on users’ online activity to gain an unfair advantage over competitors, according to the paper’s sources. The tipsters said that the emphasis is on how Facebook’s business practices affected rival social networks and online advertisers.The scope of the investigation could reportedly change before the official announcement. However, it’s believed that the Competition and Markets Authority has already identified one area it intends to focus on: the competitive impact of Facebook’s Marketplace classifieds advertising service.Marketplace is reportedly also being scrutinized by the European Commission, the European Union’s executive branch. Sources told Reuters last year that the commission was looking into whether Facebook’s large troves of user data give it unfair competitive advantage over smaller classifieds platforms with access to less information.Officials reportedly received complaints about Marketplace from several rival firms. In response, the commission is said to have sent out questionnaires to industry players asking them about the importance of customer data to their business and how their access to information compares with that of Facebook.In the case of the Competition and Markets Authority probe, investigators reportedly plan to draw on a report that the regulator published last year about the online advertising market. It concluded that “Facebook’s ability to collect a greater quantity and variety of high-quality data gives it a competitive advantage” over smaller rivals.The study was a key driver behind the U.K. government’s initiative to create a new unit within the Competition and Markets Authority focused specifically on major online platforms. The unit is expected to be tasked with ensuring platforms adhere to an upcoming competitive code of conduct. The code of conduct could, among others, mandate that companies such as Facebook give consumers the option to opt out of receiving personalized ads.The Marketplace classifieds ads service is just one component of Facebook’s online advertising business, which contributed the bulk of the $28 billion in revenues it generated in the fourth quarter. The social network and Google last year accounted for an estimated two-thirds of digital ad spending in the U.K. They’re also the two largest players in the U.S. digital ad market.