Communications Minister Stephen Conroy has rejected criticism of the Government's proposed internet filter levelled by his opposite number, Malcolm Turnbull.

The Government wants to block websites containing child pornography and other material that is refused classification.

Mr Turnbull, the Opposition's new communications spokesman, says the filter will slow internet speeds and give parents a false sense of security.

But Senator Conroy told ABC Radio's PM program that the United Kingdom, Sweden and Finland all have successful filters in place.

"Ninety-five per cent of every single internet user in the UK goes through a filter of the kind we are talking about and it blocks 100 per cent accurately the child pornography websites," he said.

"In Finland, in Sweden, in a range of Western countries, a filter is in place today, and 80, 90, 95 per cent of citizens in those countries, when they use the internet, go through that filter.

"It has no impact on speed and anybody who makes a claim that it has an impact on speed is misleading people.

"If you want to be a strict engineer, it's 170th of the blink of an eye, but no noticeable effect for an end user. So there is no impact and the accuracy is 100 per cent."

He said the Government always said the internet filter would not pick up peer-to-peer traffic, which is how the bulk of child pornography is distributed online.

But he said that did not mean the filter was pointless.

"The peer-to-peer material does nothing about the 440 child pornography sites that are there right now," he said.

"What Malcolm Turnbull has to explain to Australian families is that he is prepared to do nothing, nothing about blocking access to those 440 child pornography websites."

NBN threat

Senator Conroy says the biggest threat to internet speeds in Australia was the Coalition's policy to block the National Broadband Network (NBN).

"There is one thing though that will slow down and make the NBN more expensive and that is if Tony Abbott and Malcolm Turnbull continue to block the legislation that is before the Parliament and has been there for eight months," he said.

"If we cannot get the vote and pass this through the Parliament, then Malcolm Turnbull and Tony Abbott will be making the NBN more expensive to build and they will be causing more cable to be laid overhead than would otherwise be with the deal."

Within hours of taking on his new role on Tuesday, Mr Turnbull, with instructions to "demolish" the NBN, hit the airwaves and said the Government had not been honest about the cost of the NBN rollout.

"It is quite extraordinary that they're proposing to spend $43 billion of taxpayers' money on a project they say will result in an asset worth $43 billion, and yet they have provided no evidence, no financial analysis, no business case, no financial models to justify that expenditure or to convince any of us that this isn't going to be nothing other than a massive destruction of taxpayers' money," Mr Turnbull said on Tuesday.

"Every billion dollars that is wasted on this project - and I believe tens of billions of dollars will be wasted on this project if it goes ahead - is money that cannot be spent on fast rail, on public transport, on schools, on hospitals, on roads."

But Senator Conroy said Mr Turnbull needed to spend more time reading the $25 million McKinsey report outlining the financial viability of the NBN.

He says that in the future, there will be a big improvement in economic activity as a result of better broadband.

"There's a whole range of studies around the world that have showed in individual jurisdictions and macro studies ... when you've got broadband connected across different regions and different towns and different cities, there is significant improvements," he said.

"There are studies which my own department has released from Access Economics which talk about the advantages and the productivity of e-health, of teleworking, working from home.

"There are a range of sources ... that have looked at this case and argued that there are overwhelming macro-benefits to productivity from introducing high-speed broadband."

Senator Conroy says the copper era is coming to a close and regional Australia needs the NBN.

He says the debate is not just about download speeds but also about capacity, and Mr Turnbull is "misleading Australians" by saying they can get the same capacity on wireless networks as on a fibre network.

"If you look at the bandwidth demand worldwide, there is a massive increase in mobile; it comes off a low base but a massive increase and that's a great thing," he said.

"But the demand for fibre and fixed-line broadband capacity is equally moving at as fast if not a faster rate.

"There's plenty of information. If Malcolm takes the time to read it, he will see that fixed-line broadband is being cried out for because of the demand for the capacity of a fixed line."

Take-up debate 'irrelevant'

Reports earlier this week noted that only 50 per cent of homes in the Tasmanian towns of Midway Point, Scottsdale and Smithton had opted to have broadband fibre optic cable installed.

But Senator Conroy says the debate about take-up has become irrelevant, as eventually anyone who wants a fixed line will have to use the fibre network.

"The deal that we have with Telstra is that they are decommissioning, closing down the copper network," he said.

"To have a fixed line in what we call the 93 per cent footprint, the only way at the end of this process you'll have a fixed line is on the NBN's fibre network.

"The Tasmanian rollout is absolutely on time, exactly as we predicted, and if you go back and check the record in October last year, we said we would deliver this in the first weeks of July.

"We turned live services on in Tasmania and have customers using the NBN, we had them using it in the first week of July and it's come in 10 per cent under budget."

He says the figures of the rollout coming in 10 per cent under budget still stand.