A UK watchdog is opening an investigation into Facebook's and Alphabet's dominance of the digital ad market. 

The Competition and Markets Authority, a governmental body charged with preventing anti-competitive behavior, announced the inquiry on Wednesday. The probe will examine how Facebook and Google exploit personal data to dominate the digital advertising markets, and whether that unfairly freezes out competition. It will also further "lift the lid" on Facebook's and Google's data collection practices, the CMA wrote in a statement. 

"Much about these fast-changing markets is a closed book to most people. The work we do will open them up to greater scrutiny, and should give Parliament and the public a better grip on what global online platforms are doing," wrote CMA Chairman Andrew Tyrie.

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In Europe and the U.S., government scrutiny of tech giants' market power has intensified in recent months. 

In the U.S., the Federal Trade Commission and Department of Justice are said to be planning a sweeping antitrust probe of Facebook (FB) - Get Facebook, Inc. Class A Report , Alphabet (GOOGL) - Get Alphabet Inc. Class A Report , Amazon (AMZN) - Get Amazon.com, Inc. Report and Apple (AAPL) - Get Apple Inc. (AAPL) Report , and multiple lawmakers, including presidential hopeful Sen. Elizabeth Warren, have suggested that big tech companies could be broken up.  

Facebook and Alphabet shares closed 1.1% and 0.9% higher on Wednesday, respectively. 

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