Six trade groups - the Interactive Advertising Bureau, American Advertising Federation, the Association of National Advertisers, the 4As and two others - say they're "deeply concerned" with Apple's plans to release a version of the internet browser that overrides and replaces user cookie preferences with a set of Apple controlled standards.

The feature, which somewhat stupidly is called "Intelligent Tracking Prevention", limits how advertisers and websites can track users across the internet by putting in place a 24 hour limit on ad re-targeting. In an open letter expected to be published this afternoon, the groups describe the new standards as "opaque and arbitrary," warning that the changes could affect the "infrastructure of the modern internet", which largely relies on consistent standards across websites.

The groups say the feature also hurts "user experiences" by making advertising more "generic and less timely and useful".