The cost to internet and mobile phone users of keeping metadata for police and spy investigations has been labelled a "surveillance tax".
The federal government on Thursday introduced draft laws to parliament requiring telecommunications companies to keep metadata for two years.
While the government will make a "substantial contribution" to cover company costs, telco customers might have to make up the difference.
"It's a surveillance tax," Greens senator Scott Ludlam told reporters in Canberra.
"It's imposing a cost on people that they don't want to pay."
As well it was about introducing a regime of "mild, real-time, passive surveillance".
Senator Ludlam believes the legislation goes too far, even though he acknowledges intelligence agencies are seeking greater surveillance powers for anti-terrorism and law enforcement operations.
"At some point you have to draw a line. We are drawing the line at mandatory data retention."
Senator Ludlam warned the measure would result in a mountain of useless material as other authorities around the world had found.
"You're looking for the same number of needles in a much larger haystack."
