HOPES that a voluntary filter of child pornography will become industry standard across all internet service providers have been dealt a blow, with significant mid-sized carrier Internode declaring yesterday that it will not participate.

Communications Minister Stephen Conroy late last week announced the government would hold off on its filter proposal until a year-long review of refused classification rules had been completed.

At the same time the government said three internet service providers - Telstra, Optus and Primus, which between them represent about 70 per cent of Australian internet connections - would voluntarily block child abuse content, with the prospect that others might follow.

But yesterday, Internode declared it had significant concerns with administration of the blacklist of child porn URLs (uniform resource locators, the technical name for web addresses) used for the voluntary filter, and refused to apply it.

''It covers a tiny proportion of the content that would need to be blocked for it to be effective and has already been shown to contain URLs of legal content that Australians would expect to access,'' Internode's regulatory and corporate affairs manager, John Lindsay, said.