Michael Malone, managing director iiNet, said he would sign up to be involved in the "ridiculous" trials, which are scheduled to commence by December 24 this year. Optus and Telstra both said they were reviewing the Government's documentation and would then decide whether to take part.

But Malone's main purpose was to provide the Government with "hard numbers" demonstrating "how stupid it is" - specifically that the filtering system would not work, would be patently simple to bypass, would not filter peer-to-peer traffic and would significantly degrade network speeds. "They're not listening to the experts, they're not listening to the industry, they're not listening to consumers, so perhaps some hard numbers will actually help," he said. "Every time a kid manages to get through this filter, we'll be publicising it and every time it blocks legitimate content, we'll be publicising it."

Malone concluded: "This is the worst Communications Minister we've had in the 15 years since the [internet] industry has existed." The Government intends to introduce mandatory filtering of all "illegal material" and a second optional filter to block content deemed inappropriate for children, such as pornography.

Internet providers and the Government's own lab tests have found that presently available filters are not capable of adequately distinguishing between legal and illegal content and can degrade internet speeds by up to 86 per cent. Many ISPs already offer customers the option of switching on content filtering and the previous government provided free software filters for anyone to download from NetAlert.gov.au. Much of the opposition to Senator Conroy's plan revolves around the fact that, unlike his earlier promises, he now wants to make the filtering mandatory for all Australians - spurred on by support from vocal minorities such as the Australian Family Association and the Australian Christian Lobby.

Senator Nick Xenophon and Family First Senator Steve Fielding, both of whom the Government needs to pass legislation, have already said they want the mandatory filters broadened to include the blocking of hard-core pornography and online gambling sites. Grilled by a Senate Estimates committee in October, Senator Conroy said Britain, Sweden, Canada and New Zealand had all implemented similar filtering systems. However, in all cases, participation by ISPs was optional and the filtering was limited in scope to predominantly child pornography.

"It is happening in two other countries - China and Saudi Arabia, that's who he's lined himself up with," said Malone. In Senate question time today, Senator Ludlam asked the minister to explain those claims, but Senator Conroy dodged the question. "We are aware of technical concerns with filtering technology, and that is why we are conducting a pilot, to put these claims to the test," he said.

Senator Ludlam then asked Senator Conroy to retract the claims, as well as to explain what he meant by "unwanted content" and to "acknowledge the legitimate concerns by commentators and many members of the public that such a system will degrade internet performance, prove costly and inefficient, and do very little to achieve the Government's policy objectives". Senator Conroy said he could not answer all of those questions in the time provided and would be "happy to come back and provide the Senator with further information".