There are serious fears the privacy of everyday Australians could be in jeopardy under a data-sharing deal with the United States.
An intelligence treaty between the two nations will soon allow law enforcement agencies to share information.
The agreement will give officers rapid access to US-hosted data to fight terrorism, child exploitation and human trafficking.
It includes messaging platforms and online cloud storage in an attempt to end year-long delays in seeking evidence.
But Josh Pallas from the NSW Council for Civil Liberties said the agreement would gravely undermine privacy.
"At the end of the day our citizens shouldn't end up with less privacy rights and less human rights protections because of the implementation of this treaty," he told a parliamentary hearing on Wednesday.
Mr Pallas said the deal didn't strike the right balance.
He said defining a serious crime as one punishable by three years in prison was far too low a threshold.
The attorney-general's department previously told the committee the agreement would be a "game changer".
"I don't think we can understate the positive impact that we're expecting this to have on criminal investigations," senior official Andrew Warnes said.
The treaty must be reviewed by the Australian parliament and the US Congress before it enters into force.
