Canada's antitrust regulator is suing Alphabet's Google over alleged anti-competitive conduct in its online-advertising business, in the latest regulatory challenge to the tech giant's dominance.

The lawsuit, filed with the Competition Tribunal, follows a multi-year investigation into Google's dominance in the digital advertising market. According to the Bureau, Google holds a market share of 90 percent in publisher ad servers, 70 percent in advertiser networks, 60 percent in demand-side platforms, and 50 percent in ad exchanges in Canada.

Toronto — Canada's antitrust watchdog said Thursday it is suing Google over alleged anticompetitive conduct in the tech giant’s online advertising business and wants the company to sell off two of its ad tech services and pay a penalty. The Competition ...