BRUSSELS—Google’s plan to block a popular web tracking tool called “cookies” is anti-competitive, a group of advertisers, publishers, and tech companies said in a complaint to EU antitrust regulators. The grievance could boost the European Commission’s investigation opened in June into Alphabet unit Google’s Privacy Sandbox which the company said could allow businesses to target clusters of consumers without identifying individuals. Google said a year ago that it would ban some cookies in its Chrome browser to increase user privacy and offer the Privacy Sandbox as an alternative. The Movement for an Open Web (MOW) said the proposal would give Google the power to decide what data can be shared on the web and with whom. “Google says they’re strengthening ‘privacy’ for end users but they’re not, what they’re really proposing is a creepy data mining party,” MOW lawyer Tim Cowen said in a statement. The Commission confirmed receipt of …