Executives are fleeing web watchdog the Internet Watch Foundation (IWF) as critics accuse it of forcing through draconian new policies.
Civil rights activist Malcolm Hutty is the latest, joining three other executives in leaving the IWF which polices the internet for child pornography.
He said that he had walked out after the group's chairman, Roger Darlington, forced through a change in its policy on newsgroups which meant the IWF could ask ISPs to ban any newsgroups based simply on the name of the group.
The aim was to tighten the net on the growing problem of child porn on the web, but it is a departure for the IWF which has acted against newsgroups only where actual evidence of paedophilic material has been found.
The new rules would mean groups operating legally could suffer, Hutty said.
"I have fully supported the existing policy for the three years I have been a member. This new policy starts banning stuff that is legal. I'm disappointed by this, obviously. Unfortunately, paedophilia is such a difficult and inflammatory area, people stop thinking properly," Hutty said.
He claims the new policy was forced through without proper discussion in the group.
David Kerr, chief executive of the IWF, denies that allegation. He said: "This is a radical change for the IWF, but it's one brought about from the industry, not under pressure from the police.
"Unfortunately we had a situation where our old methods were becoming ineffective."
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