A coalition of job search sites based in Europe are issuing a complaint against Alphabet (GOOGL - Get Report) alleging anti-competitive behavior that harms their businesses. 

The complaint comes in the form of a letter sent Tuesday to European Union competition commissioner Margrethe Vestager, Reuters reported. The job search sites say that a Google tool that aggregates job listings within Google Search, placing it at the top of search results, has harmed their business by costing them users and revenue. 

In the letter, the sites asked Vestager to order Alphabet to stop the anti-competitive behavior until an investigation into the matter is complete. The signatories include the British site Best Jobs Online, German sites Intermedia and Jobindex, and others. 

The European complaint on Tuesday is the latest sign of growing antitrust scrutiny of Alphabet and other tech giants. 

In the U.S., the Department of Justice is investigating Alphabet to determine whether or not its various products and platforms stifle competition and potentially harm consumers. 

More than 90% of search results in the U.S. go through Google; in addition, it controls the Chrome browser, Android operating system, Gmail, G Suite, and a range of other dominant products in various verticals. 

At a recent House Judiciary Committee hearing on antitrust concerns in Big Tech Google's director of economic policy Adam Cohen argued that competition is "just a click away," and cited examples of specialized search sites like Travelocity for travel bookings and Amazon (AMZN - Get Report)  for product searches.

Analysts estimate that an antitrust probe of Alphabet could take roughly three years to reach an eventual conclusion. In addition to Alphabet, Facebook (FB - Get Report) , Amazon (AMZN - Get Report) and Apple (AAPL - Get Report) are all involved in antitrust probes, though not all have explicitly disclosed the investigations. 

Alphabet shares closed flat on Tuesday at $1,174.50 and are up 11% this year. 

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