ACMA's blacklist does not have a significant impact on web browsing by Australians today but sites contained on it will be blocked for everyone if the Federal Government implements its mandatory internet filtering censorship scheme. But even without the mandatory censorship scheme, as is evident in the Whirlpool case, ACMA can force sites hosted in Australia to remove "prohibited" pages and even links to prohibited pages.

Online civil liberties campaigners have seized on the move by ACMA as evidence of how casually the regulator adds to its list of blacklisted sites. It also confirmed fears that the scope of the Government's censorship plan could easily be expanded to encompass sites that are not illegal. "The first rule of censorship is that you cannot talk about censorship," Wikileaks said on its website in response to the ACMA ban. The site has also published Thailand's internet censorship list and noted that, in both the Thai and Danish cases, the scope of the blacklist had been rapidly expanded from child porn to other material including political discussions.

Already, a significant portion of the 1370-site Australian blacklist - 506 sites - would be classified R18+ and X18+, which are legal to view but would be blocked for everyone under the proposal. The Government has said it was considering expanding the blacklist to 10,000 sites and beyond. Electronic Frontiers Australia said the leak of the Danish blacklist and ACMA's subsequent attempts to block people from viewing it showed how easy it would be for ACMA's own blacklist - which is secret - to be leaked onto the web once it is handed to ISPs for filtering.

"We note that, not only do these incidents show that the ACMA censors are more than willing to interpret their broad guidelines to include a discussion forum and document repository, it is demonstrably inevitable that the Government's own list is bound to be exposed itself at some point in the future," EFA said. "The Government would serve the country well by sparing themselves, and us, this embarrassment." Last week, Reporters Without Borders, in its regular report on enemies of internet freedom, placed Australia on its "watch list" of countries imposing anti-democratic internet restrictions that could open the way for abuses of power and control of information.

The main issue raised was the Government's proposed internet censorship regime. "This report demolished the Communications Minister's contention that Australia is just following other comparable democracies," Greens communications spokesman Senator Scott Ludlam said.

"We are not. The Government is embarking on a deeply unpopular and troubling experiment to fine-tune its ability to censor the internet. "I agree with Reporters Without Borders. If you consider this kind of net censorship in the context of Australia's anti-terror laws, it paints a disturbing picture indeed." EFA said the Government's "spin is starting to wear thin" and it could no longer be denied that the ACMA blacklist targets a huge range of material that is legal and even uncontroversial.

The Communications Minister, Stephen Conroy, has repeatedly claimed his proposed mandatory filters would target only "illegal" content - predominantly child pornography. "As time goes on, pressure will only mount on the Government to expand the list, while money and effort are poured into an enormous black box that will neither help kids nor stem the flow of illegal material," EFA said.

"If the minister truly believes that children are seeking out, or being bombarded with, child pornography, then there's a dearth of both common sense and proper research in the ministerial suites." Already, the head of the Australian Christian Lobby, Jim Wallace, has said he hopes the sex industry will go broke as a result of the censorship scheme. Independent Senator Nick Xenophon previous expressed his desire to have online gambling sites added to the blacklist but has since withdrawn his support for the scheme, saying it was dangerous and could be "counter-productive".

The Greens and Opposition also oppose the scheme, meaning any legislation to implement it will be blocked. The Opposition has obtained legal advice that "legislation of some sort will almost certainly be required", but others have said it may be possible to implement the scheme without legislation.

Speaking at a telecommunications conference last week, Senator Conroy urged Australians to have faith in MPs to pass the right legislation. Despite previously saying his scheme would be expanded to block "refused classification" content that includes sites depicting drug use, sex, crime, cruelty and violence, he said opponents of his plan were spreading "conspiracy theories". The Government's internet censorship trials are due to begin shortly but critics have said they may not provide much useful data on the real-world implications because none of the major ISPs were chosen to take part.