Prime Minister Julia Gillard says she is happy with the policy aim of the Government's proposed internet filter, but understands there are concerns about it.

The Government plans to introduce a mandatory filter to block sites that contain illegal material.

Ms Gillard says images of child abuse or child pornography should not be accessible on the internet.

But she has acknowledged the concerns raised by critics of the plan.

"I understand that there's a set of concerns, technical concerns about internet speed, and also concerns that this somehow [moves] into taking away legitimate use of the internet," she said.

"It's not my intention that we in any way jeopardise legitimate use of the internet."