Communications Minister Stephen Conroy has conceded that a Classification Board review could "substantially" change the proposed mandatory internet filter.

The Classification Board is set to review its standards in what makes up refused classification (RC) rated content.

Senator Conroy told triple j's Hack that the review could change the filter "substantially".

"We've done the tests on speed, now we're going through a process to see what is contained within RC and we're happy to live with the outcome of that and it could change substantially," he said.

"The Classification Board is independent of Government and ultimately will be deciding through that process what the RC category is."

But Senator Conroy also says he sometimes disagrees with the board's decisions on offensive material.

"The Classification Board is independent of governments. They've been doing these things and sometimes they make mistakes," he said.

"Sometimes they classify things and I think 'that should be a higher classification, that should be a lower classification' and I'm sure you would do the same.

"But they're independent of Government and they make these judgments."

Senator Conroy is determined to introduce Labor's mandatory filter, despite mounting criticism from internet users who say it will slow download speeds and cause unwarranted censorship.

"If you look overseas where many countries have voluntarily introduced the exact filter that we're talking about - all of the claims that many people have made about the impact on speed have been false," Senator Conroy said.

"There's no silver bullet when it comes to cyber safety. We have a comprehensive cyber safety package of which the filter is a part."

But the Coalition says it would ditch the filter and instead spend $60 million on providing internet-filtering technology free to families.

Earlier in the election campaign, Opposition treasury spokesman Joe Hockey said the filter plan was a "flawed policy".

"We believe the internet filter will not work," he said.

"It is not going to capture a whole lot of images and chatter that we all find offensive... that are going through email."

The Government had originally intended to introduce the legislation in the first half of this year, but then deferred it to later in 2010.