An Internet Corporation for Assigned Names and Numbers (ICANN) chief has said the Australian government will “embarrass itself” if it pushes ahead with plans to install a national Internet content filter.

The group is a non-profit corporation that oversees management of domain names and IP addresses, Internet Protocol address space allocation and generic Top Level Domains.

ICANN board chair Peter Dengate Thrush said national Internet content filters are ineffective at law enforcement. The plan was introduced by federal Communications Minister Stephen Conroy ostensibly as a mechanism to control distribution and access to child pornography.

“The government has set itself up for embarrassment,” Thrush said.

“I have no problems with the principle behind it [but] censoring material outside the country is difficult and the tools to do it cost a lot.”

Web filtering at the Internet Service Provider-level will be compulsory under the plans, and all online illegal and Restricted Content will be blocked.

In a previous development, Conroy refuted claims that political material could be added to the government-controlled blacklists, but acknowledged the public has raised legitmate concerns about functional-creep.

"It goes against the tenets of the Labor Party to block political [material]," Conroy said on a previous ABC Q&A television program.

The federal government is conducting trials with nine ISPs to evaluate the effectiveness of the filters and will make a decision pending the results.

Netforce, Tech2U, OMNIConnect, Webshield and Nelson Bay Online are using a Marshal836 filtering and reporting product for the trial. Primus Telecommunications, Highway 1, Optus and Unwired are also participating in the government pilot.

Critics have raised concerns that a national Web filter program will impose heavy costs on ISPs and argue the technology will be unable to fulfill the government's objective of blocking illegal content.

The filter could potentially be bypassed by technologies such as anonymous proxies such tor and Virtual Private Servers.

A recent independent trial by ISP Exetel found Web filtering could cost users about $6 a year and cause no network disruption.