AUSTRALIA will next month become one of the few democratic nations to censor the worldwide web.

But the censorship will not be overseen, legislated or even enforced by the Federal Government.

More than 500 websites will instead be blocked voluntarily by two of the country's largest internet service providers and two smaller firms.

The voluntary filter - an interim move before the Gillard Government reintroduces mandatory internet filter legislation next year - will deal only with child-abuse websites and not all "refused classification" material.

Some law experts are celebrating the introduction of the voluntary filter, calling it a "public service".

But free speech and internet experts have questioned the censorship plan, demanding details about the sites to be banned and labelling it a "cosmetic" approach that will offer users only "a false sense of security".

The plan to have internet service providers voluntarily block websites from July was proposed by the Government last year, after its larger censorship plan was postponed, pending a classifications review.

Funding of $9.8 million was set aside to help block "refused classification" material for users on a commercial basis.

But the Federal Government last month dropped $9.6 million from this scheme, citing "limited interest in the grants" from the industry.

Telstra, Optus and Primus committed to blocking child-abuse websites only and spokesmen from Telstra and Optus tell Switched On the ban will begin soon.

A Telstra spokesman says the company is continuing work "to implement our voluntary commitment of last year", while an Optus spokesman says the company will share "more information on this in the coming weeks".

Two small carriers, Webshield and ItExtreme, have also committed to blocking the sites.

The introduction of the internet filter will make Australia one of the few world democracies to censor the worldwide web.

A similar scheme was introduced in the UK by British Telecom in 2006, blocking sites decreed offensive or potentially illegal by the Internet Watch Foundation.

But the plan fell into controversy in 2008 when the IWF blacklisted a Wikipedia entry on a band called Scorpions, calling one of the band's album covers "potentially illegal".

UTS Communications Law Centre director Michael Fraser admits any internet filter will leave "opinions sharply divided", but blocking child-abuse URLs should be supported by Australian internet users.

System Administrators Guild of Australia board member Donna Ashelford says the ISP ban will be technically preferable to the Government-proposed filter because it will block only website addresses rather than general web content and will not noticeably slow down access.

Ashelford, however, calls the filter a "cosmetic" ban because it will be easy for webmasters to circumvent and it will not tackle the more common sources of child-abuse material.

"You're talking about a small number of fixed URLs so the impact on internet speed will be trivial," she says. "Unfortunately its effectiveness will be trivial as well, because if you're just blocking a single website address, a person can get around it by changing that address with one character."

Ashelford says the scourge would be better tackled by law enforcement and by parents educating their children.

"Parents should teach their kids to use the internet just as they teach them to cross the road," she says.