Ludlam questioned Conroy's comparison of Australia as following other countries such as the UK, Canada and New Zealand where filtering of blacklist material had been introduced.

"It got really muddy around the subject of what other countries were doing, and what would be considered mandatory and what would be opt-out. He really muddied the waters on the countries that they are trying to compare us to. My understanding is not a single one of them has instituted or even seriously tried to institute mandatory content blocking. As far as I am aware they are all trialling optional content blocking," he said.

"None of them are really having a proper go at mandatory filtering. When you look at the countries that are attempting mandatory filtering of "illegal" content on the Net, it's a very different set of countries: China, Burma, the UAE and other places."

One gaping chink in Conroy's filtering armor is its inability to block data transferred over peer-to-peer networks, which is estimated to account for upwards of 60 percent of all Internet traffic.

"A lot of material on the Net isn't live as such, it's being exchanged on peer-to-peer networks and the kind of stuff we're talking about here isn't going to touch that, so that's a large volume of traffic that is just going to go under the radar, and the mandatory content blocking scheme is going to be drawing resources away from probably more useful law enforcement activities," Ludlam said.