Bhati said critics should not pre-judge the capabilities of the content filters until results are available from the trials.

The "hundreds of thousands" of iPrimus customers will have the option to participate in the trials without the need to pre-register.

Perth-based ISP Highway1's general manager Nick Power said an initial 50 customers have opted-in to the trial.

"We have only just e-mailed our general customer base [of 3000] asking if they wish to participate. On current feedback, we are receiving about a 40 percent positive and 60 percent negative participation rate for those that have responded to the e-mail," Powers said.

Some 98 percent of Highway1 customers are SOHOs and SMEs spread across the country.