Federal Communications Minister Stephen Conroy has given a pre-election undertaking not to broaden the Government's proposed level of internet censorship.

Senator Conroy says the scope of the content covered by the Government's proposed mandatory filter will not be widened by a future Labor government.

"We're making it very clear, this is our policy: refused classification only," Mr Conroy told the ABC's Four Corners program.

"If a majority of the Parliament in the future want to broaden the classification, well then, Australians should stand up and say 'just a minute', and I'll be one of them."

Eighteen months ago Senator Conroy galvanised his critics by suggesting that the scope of a mandatory internet filter would include any online material that was deemed to be "prohibited content" by the Australian Communications and Media Authority (ACMA).

"You can't opt in or out of the prohibited material," he said at the time.

Prohibited material includes not just Refused Classification and X-rated content, but also any R-18+ and MA-15+ content that is not protected by an ACMA-approved age-verification gateway restricting access to underage users.

However, last December, Senator Conroy announced the revised secret blacklist of material to be censored by internet service providers (ISPs) would be limited to individual webpages that had been refused classification by the Classification Board.

Refused classification material includes child pornography and detailed instruction in crime or drug use.

But it also includes any material that the Classification Board judges will "offend against the standards of morality, decency and propriety generally accepted by reasonable adults".

Critics of the mandatory filter say the category is far too broad.

Polarised debate

Jim Wallace of the Australian Christian Lobby says he finds it "quite amazing" that anyone would oppose the filter plans.

"The material that the Government is looking to block is illegal material," he told Four Corners.

"I think if people believe that they should be using child pornography, bestiality material, sexual violence or instructions to crime, then really somebody somewhere should be raising a file on them.

"The bigger principle here is to establish the principle that the internet is not a free zone and I think that given the movement of technology and given the expectation of society that what the Government is proposing is therefore a good solution."

On the other side of the debate, Google Australia's head of policy, Iarla Flynn, says the proposed mandatory filter goes too far.

"It's a heavy-handed measure," he said.

"Our primary concern is that the scope of content which the Government is seeking to block is too wide. Remember, this would apply to every internet user in Australia, whether they like it or not."

Legislation to introduce a mandatory internet filter is unlikely to come before Parliament before the next election. But Senator Conroy has made it clear he remains committed to its introduction.

Blacklist concerns

Critics of the filter point to several examples of web content that they say could be blocked under a mandatory filter.

Pages about safe injecting and sites giving tips on how to create graffiti are among those that could be blocked.

Senator Conroy told Four Corners he will not be deciding what is on the list.

"Individual pages will be determined by - at arm's length from government - by the Classification Board, as it should be," he said.

"Stephen Conroy and the Government do not make the individual decisions."

Also liable to be blocked are web pages giving advice on assisted suicide.

The online version of the Peaceful Pill Handbook, written by euthanasia campaigner Philip Nitschke, has been refused classification.

It can be accessed online from Australia now because the website is hosted overseas. Under a mandatory filter however, it will be blocked from view here, but remain visible to internet users overseas.

Critics of the filter say elements of some extremely popular adult websites may also be censored in future.

The vast majority of adult material on the internet is hosted overseas, and is not directly regulated by ACMA.

One adult film which could be blocked online is called Pirates II: Stagnetti's Revenge. Fiona Patten of the Australian Sex Party describes it as "a very mainstream adult film".

This film, which is hosted on websites across the world, is sold in Australian sex shops in two separate parts because it depicts sexual acts, and because there is also violence in the film.

But Ms Patten argues the violence is not sexual violence.

"We're talking cartoon ghosts, cartoon skeletons fighting and pirates having sword-fights," she said.

"So all of that sort of action and adventure scenes had to be put into one disc, and all of the sex scenes put into another disc. This is the only country in the world where this film is split like this and has to be seen separately."

Ms Patten says that if attempts had been made to sell the film unedited it would have been refused classification.

The Classification Board confirmed this view.

"Within the context of actual sex, violence cannot be accommodated, and therefore the film, if it contained actual sex and violence, would have been refused classification," it said.

In future Ms Patten argues every website where the film can be viewed will be liable to be blocked by the Government's mandatory filter.

Election promises

Other critics of the policy, speaking on Four Corners, point to the policy changes that have occurred since Labor announced a family-friendly cyber-safety policy before the last election.

That policy promised that: "A Rudd Labor Government will require ISPs to offer a clean feed internet service to all homes, schools and public internet points accessible by children, such as public libraries.

"Labor's ISP policy will prevent Australian children from accessing any content that has been identified as prohibited by ACMA, including sites such as those containing child pornography and X-rated material."

The Government has now accepted that it will not be possible to mandate ISPs to provide a broad-brush clean feed internet service in this way.

In defending its current policy to limit the scope of censored online material to content which has been refused classification, Senator Conroy concedes that "if you try and do a broader range of things at the mandatory level, then you are likely to have a serious impact on the speed of the internet".

Colin Jacobs, vice-chair of Electronic Frontiers Australia, says the current plan has no cyber-safety benefit and is a clear move away from the policy Labor originally promised.

Chief executive of the Internet Industry Association Peter Coroneos agrees.

"A lot of the content that families really are concerned about for their children - things like violent material, racial hatred material, material which promotes race hate, maybe even just adult content that you wouldn't want your children to see - none of that will be picked up by this filtering solution," he said.

Voluntary scheme ruled out

The Government has also conceded that it will not be able to censor high-traffic websites like YouTube and that the filter will be possible to circumvent.

Even so, Senator Conroy is refusing to follow the example of other countries, such as the UK, Canada and New Zealand, by agreeing to limit the scope of the filter to child pornography and by allowing ISPs to filter out child pornography on a voluntary basis.

Mr Coroneos told Four Corners he has approached the Minister offering a voluntary scheme.

"We've actually approached the government on several occasions to propose a solution that would be consistent with best practice in other jurisdictions," he said.

"But for whatever reasons, the government is intent on pursuing a legislative course here."

Senator Conroy is determined to legislate.

"They don't need me to invite them, firstly, they could just do it," he said.

"They could have announced it five years ago. They could have announced it 10 years ago. They could have announced it yesterday. They've got a policy opposing any form of voluntary ISP filtering of anything."

Senator Conroy told Four Corners he and the United States Government are "going to agree to disagree" on the issue of a mandatory internet filter.

The US State Department has raised concerns about the proposal with the Australian Government.

While standing firm on his intent to legislate, Senator Conroy does concede that he has been troubled by the secrecy of the blacklist which will contain the list of webpages to be blocked if a mandatory filter is introduced.

"One of the things I've really struggled with, genuinely struggled with, is this argument that you should publish the list," he said.

"Because unlike with books or movie titles, when you publish those you don't give access to the material.

"The problem is if you publish a webpage address, you give direct access to the material."

Watch the full report on tonight's Four Corners at 8:30pm on ABC1.