The Greens say the Federal Government's decision to delay the introduction of its mandatory internet filtering program proves the policy is flawed.

The plan to block sites containing "refused classification" material has been criticised by internet user groups who argue it will not work and will slow download speeds.

Communications Minister Senator Stephen Conroy announced today an independent review of the policy to look at what makes up "refused classification" rated content.

He says the review, to take up to a year, has nothing to do with criticism of the proposal from the likes of Google and the US government.

"Internationally, this is what happens in many, many countries," he said.

"This is not out of the ordinary and if you are a supporter of the civil society, of which I am, the civil society is not an unregulated wild west."

Greens Senator Scott Ludlam says there appears to be several reasons for the change.

"We have got a leadership change, we have got an election looming and they are trying to clear away bad news," he said.

"This issue has been a real source of bad news for the last 18 months and I think also we are seeing an acknowledgment of the deep flaws in the proposals.

"Finally we are actually seeing some acknowledgment that critics of the filter have been right all along."

Senator Ludlam says the original policy would not have been effective.

"Most of the really toxic material is not actually traded on live websites on the world wide web - it's on the darknet and it's on places where the filter simply won't be able to reach," he said.

"That has been one of the strongest criticisms of the filter - it's nowhere near addressing the concerns that the Government claims to hold."

'It's absurd'

Colin Jacobs, the chairman of Electronic Frontiers Australia, says it is pointless to apply classification guidelines to the internet.

"The classification scheme is long overdue for a major rethink on how it can be applied in the internet age," he said.

"It was designed for books and films and movies.

"The internet operates on a matter of minutes or seconds so having a board of government censors look at web pages ... it's absurd when you think about it."

Mr Jacobs says censorship rulings will be obsolete by the time they are issued and will be easily circumvented.

He says filters which do not rely on classification are much more effective.

"When parents put a filter on their home computer for their children, it's not based on classification," he said.

"It looks at the content in real time to decide if it's appropriate for their kids.

"The parents can decide what criteria are in use there. This is clearly more appropriate and more effective from a cyber-safety point of view."