A war of words has erupted again over the Federal Government's plan to bring in a mandatory internet filter and this time internet giant Google has been dragged into the fray.

Legislation to introduce the filter is expected in the coming months and Communications Minister Stephen Conroy hit the ABC's airwaves on Monday night to defend the Government's plans to blacklist offensive material.

But the Minister's many critics, including internet and software companies, say the Government's plans now amount to censorship.

Senator Conroy has tried to deflect the criticism, taking aim instead at Google over its censorship policies.

During a 50-minute radio program on the ABC, Senator Conroy launched a vehement defence of the Government's plans to block access to certain websites.

"This is material that includes child sexual abuse material, bestiality, sexual violence including rape, instruction in crime and terrorist acts," he said.

"You can't get it in a library today, you can't buy it in a newsagency, you can't get it on DVD and you certainly can't see it at the cinema or on your TV.

"And it's currently banned already by the blacklist that was introduced nine years ago and it's banned on Australian-hosted websites today."

Several internet and software giants say the filter simply will not work, while Colin Jacobs from Electronic Frontiers Australia says parents will be lulled into a false sense of security.

"The filter that we're looking at does not include R-rated material. It does not include X-rated material. These things are explicitly excluded from the filter," he said.

"Therefore, it really won't have any effect whatsoever on the safety of children online, nor will it address any of the real cyber safety risks that have more to do with bullying and interactions with peers and what-not.

"But it comes at a great cost in terms of taxpayer funds and the enormous costs in terms of our free speech."

The US government yesterday added its voice to the anti-censorship campaign, with the US State Department announcing it had raised the issue with Australian officials.

Swipe at Google

Senator Conroy says his department has not been directly contacted by US officials, but in the final seconds of last night's discussion he took a swipe at Google for some of its policies on content, privacy and censorship.

"Not withstanding their alleged 'do no evil' policy, they recently created something called Buzz and there was a reaction. People said 'well, look aren't you publishing private information?'," Senator Conroy said.

"The founder of Google said the following: 'If you have something that you don't want anyone to know, maybe you shouldn't be doing it in the first place'. He also said recently to Wall Street analysts: 'We love cash'.

"So when people say 'shouldn't we just leave it up to the Googles of this world to determine what the filtering policy should be?' - make no mistake, anybody who wants to go onto Google's sites now and look up their filtering policy will actually find they filter more material and a broader range of topics than we are proposing to put forward.

"I'll back our Parliament to stand fast on these issues from Google."

A spokeswoman for Google has issued a statement to the ABC saying: "We were surprised to hear the Minister try to make this an issue about Google. This is a debate about freedom of access to information for all Australians, an issue of national importance. Let's focus on that."

Google has made a submission to the Government's discussion paper on the internet filter. It does not support the plan, saying the scope of content to be filtered is too wide.

Blacklist

Other critics have seized on the fact that the Government will refuse to make public the names of the blacklisted sites.

Information security expert Dr Jarrod Trevethan says the blacklist will not work.

"Perpetrators of child pornography will look for other means to access and distribute content. And as computing devices become more pervasive, there are more options available for concealing and transmitting content," he said.

"Perpetrators will find alternative methods to access the site. For example, by contacting someone in another country who can access the blocked site and then having them transmit it directly to them."

And Dr Trevethan is critical of the Government's determination to keep the blacklist under wraps.

"If a security system can withstand public scrutiny over time then confidence in the system will grow. Keeping the security mechanisms secret will only cast doubt over its real effectiveness," he said.

"So unless this is a matter of national security, the Government should be completely open about process."

Senator Conroy says making the list of banned sites public would defeat the purpose of the blacklist, but he concedes transparency is important and there may need to be an independent body to monitor the filter.

In any case, the filter will not go ahead without the support of the Federal Opposition, which says it is yet to be convinced that the mandatory filtering plans will actually be effective or achieve the best results.