The decision was called "obscene" by Karl Auerbach, former board member of Icann which approved the .xxx plan.

Mr Auerbach said Icann should be giving priority to socially positive domain name proposals rather than helping pornographers profit.

The decision was also called "dangerous" by net privacy campaigner Lauren Weinstein, who said it could provoke censorship problems for years.

Critical path

The plan to create the .xxx domain received its blessing from the Internet Corporation for Assigned Names and Numbers (Icann) earlier this week. The decision was a surprise because the idea has been floated and roundly rejected several times over the last five years.

Writing in his blog and in an open letter to Dave Farber's well-known mailing list, Karl Auerbach took Icann to task for its decision.

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In light of this, Mr Auerbach said Icann should concentrate on socially constructive domains first rather than pandering to pornographers.

In his blog he asked: "Why should .xxx get precedence over schools, churches, civic groups, aboriginal communities, labor organizations, and artistic groups?"

Mr Auerbach said Icann already had many proposals for new domains from many groups that could actually contribute to the value of the internet.

He pointed out that more than 50 organisations have submitted proposals to Icann for new net domains but, so far, only seven of those have actually been created.

Mr Auerbach predicted that the .xxx domain would encounter problems in defining which sites should sit in the new domain.

Sex ghetto

This question of how to categorise sexual websites was picked up by Lauren Weinstein, a well-known net privacy campaigner.

Also in a letter published on the IP mailing list, Mr Weinstein said "the existence of dot-ex-ex-ex is likely to create a political and litigious firestorm."

He predicted that the setting up of the domain would bring about attempts to shoe-horn all sexual sites into the .xxx domain and provoke huge rows about just what counts as an "adult" site.

Although some outright porn sites will be happy to move to the .xxx domain, others that only have some "adult" content on their pages could be much more reluctant.

Mr Weinstein said the religious right in the US might be motivated to make any site with any "adult" content move to the .xxx domain.