Internet search giant Google has come out in opposition to the Federal Government's push to introduce mandatory ISP filtering.

In a post on Google Australia's official blog, the company said the plan raised concerns about censorship.

"At Google we are concerned by the Government's plans to introduce a mandatory filtering regime for Internet Service Providers (ISP) in Australia, the first of its kind amongst Western democracies," the post said.

"Our primary concern is that the scope of content to be filtered is too wide."

While Google accepted there must be some limits on internet content, it condemned the Government's filtering approach as heavy-handed.

"We have a bias in favour of people's right to free expression," the post said.

"While we recognise that protecting the free exchange of ideas and information cannot be without some limits, we believe that more information generally means more choice, more freedom and ultimately more power for the individual.

"Some limits, like child pornography, are obvious. No Australian wants that to be available - and we agree. Google, like many other internet companies, has a global, all-product ban against child sexual abuse material and we filter out this content from our search results.

"But moving to a mandatory ISP filtering regime with a scope that goes well beyond such material is heavy-handed and can raise genuine questions about restrictions on access to information."

Citing a recent report into filtering, Google said the use of refused classification (RC) as a screening tool would go far beyond restricting illegal content.

"The recent report by Professors Catharine Lumby, Lelia Green and John Hartley - Untangling The Net: The Scope of Content Caught By Mandatory Internet Filtering - has found that a wide scope of content could be prohibited under the proposed filtering regime," the post said.

'Grey realms'

"Refused classification 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.

"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."

But the Federal Government maintains the new filter rules are not intended to curtail freedom of speech.

Google said the Government should instead focus on education and providing effective filtering tools for individuals.

"While the discussion on ISP filtering continues, we should all retain focus on making the Internet safer for people of all ages," the post said.

"Our view is that online safety should focus on user education, user empowerment through technology tools, and cooperation between law enforcement and industry partners. The Government has committed important cyber safety education and engagement programs and yesterday announced additional measures that we welcome."

Google also defended weighing into the controversy, saying discussion on contentious issues was needed for effective democracy.

"Exposing politically controversial topics for public debate is vital for democracy," it said.

"Homosexuality was a crime in Australia until 1976 in ACT, NSW in 1984 and 1997 in Tasmania. Political and social norms change over time and benefit from intense public scrutiny and debate.

"The openness of the internet makes this all the more possible and should be protected.

"The Government has requested comments from interested parties on its proposals for filtering and we encourage everyone to make their views known in this important debate. "