Andrea Coscelli, chief executive of the CMA, said: “We intend to thoroughly investigate Facebook’s use of data to assess whether its business practices are giving it an unfair advantage in the online dating and classified ad sectors.
“Any such advantage can make it harder for competing firms to succeed, including new and smaller businesses, and may reduce customer choice.
“We will be working closely with the European Commission as we each investigate these issues, as well as continuing our coordination with other agencies to tackle these global issues.”
A Facebook spokesman said: “We are always developing new and better services to meet evolving demand from people who use Facebook. Marketplace and Dating offer people more choices and both products operate in a highly competitive environment with many large incumbents. We will continue to co-operate fully with the investigations to demonstrate they are without merit.”
This is the third investigation into a suspected breach of competition law the CMA has opened in digital markets. It is also investigating Google’s “privacy sandbox” and Apple’s AppStore.