Former High Court judge Michael Kirby. Nearly 120,000 Australians signed a petition against internet censorship by online activist group GetUp. In an interview with Fairfax Radio this morning, Kirby said some circles feared the controversial policy would be "the thin end of the wedge of the Government moving in to regulating the actual internet itself". "Once you start doing that you get into the situation of Burma and Iran where the Government is taking control of what people hear and what information they get," he said, adding that Australia's approach hadn't been attempted anywhere else in the world.

Google has also entered the debate, saying yesterday the scope of the content to be filtered went too far beyond child pornography and that the "heavy handed" approach would restrict freedom of expression.

"Refused Classification (or RC) is a broad category of content that includes not just child sexual abuse material but also socially and politically controversial material - for example, educational content on safer drug use - as well as the grey realms of material instructing in any crime, including politically controversial crimes such as euthanasia," Google Australia's head of policy, Iarla Flynn, said. "This type of content may be unpleasant and unpalatable but we believe that government should not have the right to block information which can inform debate of controversial issues." Kirby and Google's concerns mirror that of Sydney University Associate Professor Bjorn Landfeldt, who said yesterday that there was no clear definition of "refused classification" and the goalposts dictating what content is prohibited could be substantially widened in future. Already, the refused classification category includes a significant proportion of legal material such as regular gay and straight porn sites, fetish sites, euthanasia material and innocuous sites that have been mistakenly prohibited. "It was through 'public complaints mechanisms' like the one Conroy is proposing, that classic literature such as , and were once banned in Australia," GetUp said.

Conversely, the Australian Christian Lobby has said it wants the filters broadened to cover all X- and R-rated content on the internet, with people having to opt-in to receive this material. Landfeldt also criticised the pilot trial report used by the Government to justify the policy, saying the trials were designed to succeed from the outset, presented no new information and were now being used by the Government to further its political agenda. The Government has said 15 other Western democracies have implemented the same filtering plan but most of the other countries have made the scheme voluntary for ISPs and the blacklisted content is limited to child pornography. "Australia's proposed regime would uniquely combine a mandatory framework and a much wider scope of content, the first of its kind in the democratic world," Flynn said. In a phone interview, Flynn said it was too early to say what effect the filters would have on Google's services but "if you were to look at YouTube today and ask: 'Is there material on YouTube which could be considered refused classification?', the answer would have to be 'yes' ".

Conroy's policy has attracted significant ridicule from international commentators and media, with news headlines such as "Australia plans Chinese-style internet filtering" and "Joining China and Iran, Australia to filter internet" appearing on the Telegraph.co.uk and FOXNews websites. The Greens are expected to oppose the Government's censorship legislation, while Family First Senator Steve Fielding has said he would support it. The Coalition has expressed "concerns" about the filtering scheme but it is believed the conservative leadership team would have difficulty opposing legislation designed to protect children online. Liberal leader Tony Abbott said he was "open to proposals" yesterday but two Liberal backbenchers, Jamie Briggs and Alex Hawke, have already committed to opposing the policy.

"While our reservations about the effectiveness of the proposal are strong, we will examine and assess the detail as we have consistently said we would," Opposition communications spokesman Tony Smith said.