Ben Williams, operations and communications manager at AdBlock Plus. Adblock Plus President and CEO of the Interactive Advertising Bureau (IAB) Randall Rothenberg used the opening keynote speech at the IAB summit to accuse Adblock Plus of being an "unethical, immoral, mendacious coven of techie wannabes" and an "old-fashioned extortion racket."

The vitriol came after Adblock Plus complained that it had been "disinvited" from the summit for no reason. The annual IAB conference hosts the biggest names in the digital-advertising industry. Adblock Plus attended last year and it was registered for this year's event, but its registration was cancelled by organizers.

"We had never invited them in the first place," Rothenberg said on Monday. "They registered for this event online. When we found out, we cancelled the registration and reversed their credit card billing. Why? For the simple reason that they are stealing from publishers, subverting freedom of the press, operating a business model predicated on censorship of content, and ultimately forcing consumers to pay more money for less – and less diverse – information."

Adblock Plus allows users to block digital advertising. Publishers and advertisers are particularly unhappy about AdBlock Plus' plan to generate an "Acceptable Ads" platform. This would let a brand subvert the ad blocking if it paid a fee and its ad meets specific criteria.

Rothenberg went further by accusing adblockers in more general terms of illegality: "Many of their business models are undoubtedly illegal. Already, Shine’s model of ISP-level ad-blocking has been cited by regulators as a probable violation of net neutrality principles," Rothenburg said.

Rothenberg was speaking at the opening IAB keynote on Monday IAB

Hitting straight back, on the same day as Rothenberg's speech, Shine CMO Roi Carthy called the IAB irrelevant to customers in a piece for Ad Age titled, "Consumers Must Look Elsewhere Than the IAB for Protection."

Business Insider contacted Ben Williams, operations and communications manager at AdBlock Plus for a response, but he declined to comment directly on Rothenberg's attack. Though he did add: "As ever, we remain interested in discovering better, more sustainable ways for publishers and content creators to get paid. And we invite anyone and everyone to join us in doing so."

Rothenberg's full speech, in which he waxes lyrical about the links between consumerism, freedom of advertising, diversity and freedom of speech, can be read here.

Last week, tracking blocker Ghostery accused AdBlock Plus of extortion. Willams responded to these accusations in an email to Business Insider: "What we're doing isn't extortion. No one has to take part in Acceptable Ads, and those that do have to maintain criteria for better ads. Furthermore, Acceptable Ads is constantly improving — we just improved the criteria and are looking forward to giving control over to an independent committee."