Rob Norman, the chief digital officer of the world’s biggest media buying company, GroupM, has ripped into the recent Association of National Advertisers (ANA) report on media agencies rebates, saying it overlooked the fact that agencies make major investments in technology at their own risk.

The long-anticipated ANA report, which last week published the results of an eight-month probe into the sector by investigations firm K2, alleged secret rebates and other non-transparent business practices are “pervasive” in the agency sector.

Read the full Business Insider article here.