The Australian government has postponed its plans to introduce a national internet filter that has been criticised as web censorship.

Stephen Conroy, the communications minister, said on Friday that introduction of the "Clean Feed" filter would be delayed for a review of what material should come under the initiative.

"Some sections of the community have expressed concern about whether the range of material included in the Refused Classification [RC] category, under the National Classification Scheme, correctly reflects current community standards," Conroy said in a statement.

"In order to address these concerns, the government will recommend a review... be conducted at the earliest opportunity. The review would examine the current scope of the existing RC classification, and whether it adequately reflects community standards."

Conroy said the mandatory filter would not be imposed until completion of the review, which could take up to a year.

Friday's move buys the government a reprieve in protests and neutralises what would have been a potentially contentious topic as it prepares to call an election in the coming weeks.

Voluntary block

While the review is under way, three of Australia's largest internet service providers, Telstra, Optus and Primus, agreed to voluntarily block a government-compiled list of online child pornography material.

Conroy said he welcomed "the socially responsible approach taken by some of Australia's largest ISPs" - accounting for about 70 per cent of internet users - to voluntarily block the webpages, which he described as featuring "abhorrent" content.

The government's plan to block access to sites featuring material such as rape, drug use, bestiality and child sex drew criticism from firms such as Google, Yahoo! and Microsoft.

Angry user groups launched an online campaign accusing the government of censorship, while cyber-activists succeeded in jamming key government websites in a concerted campaign of protest hacking.

User advocates, the pornography industry and others have likened the proposed system to official firewalls operating in countries such as China and Iran.

But Conroy remained adamant that the filter proposal did not constitute censorship.

"I don't think any Australian actually tries to describe blocking child pornography or bestiality or pro-rape websites as censorship," he said.