The media conglomerate controlled by Rupert Murdoch is joining the fray in Google's protracted European antitrust case, saying the technology company unfairly distorts competition.

Robert Thomson, CEO of New York-based News Corp., says in a letter to the EU's antitrust authority that Google is "willing to exploit its dominant market position to stifle competition." He says it systematically diverts users away from relevant search results to its own offerings.

Thomson says his company—whose outlets include The Wall Street Journal and the New York Post—also sees a lack of willingness by Google to curb content piracy.

In the letter released late Wednesday but dated Sept. 8, Thomson welcomes the EU's recent decision to demand stronger concessions from Google to reach a settlement in the four-year-old case.