The crossbenchers have provided the "true opposition" to the government's proposed data retention regime, Greens Senator Scott Ludlam told a press conference earlier today.
Ludlam was joined by independent Senator Nick Xenophon and the Liberal Democratic Party's Senator David Leyonhjelm.
"On a bill as important as this, the Labor party has practically vacated the field [and] provided no contribution to the debate this morning," Ludlam said.
The data retention bill is currently in the Senate and is expected to be passed with Labor's support sometime tonight or early tomorrow.
In addition to opposing the bill outright, the Greens have sought to make a number of amendments to it.
"What we're dealing with is a bill that is open ended in scope, open ended in cost and open ended in consequence," Ludlam said.
"It's a bill for mandatory preservation and capture of data and we finally had an admission from the attorney general this morning that it will catch material that's not presently being stored [by telcos].
"It will impact and hit the industry unevenly depending on size and capability of different companies and we've identified gaping loopholes and flaws in the bill. It should have been sent back to the drawing board long before it got to us."
Leyonhjelm said he disagreed with "many aspects" of the government's bill.
"It's the government that should be watched, not the government watching the public," the libertarian senator said.
The government earlier in the day rejected an amendment moved by Leyonhjelm that would have limited the mandatory data retention period to three months instead of two years.
"The data retention period shouldn't be two years," Leyonhjelm said.
"There are commercial reasons why some ISPs retain data for three months — if they're going to legislate anything that would be a better option."
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Although the attorney-general has said the use of data retained under the scheme will be restricted to serious crimes such as terrorism, "there is nothing in the bill that will restrict it to those things," the senator said.
"I think it's fair to say you couldn't find a more disparate group of pollies," Xenophon said of the crossbench alliance against the data retention bill.
"These concerns are not ideological — they are about basic issues of good government and citizens being given certain rights."
Xenophon said he was particularly concerned about the impact of data retention on journalists.
"This metadata crackdown is a mega mess when it comes to press freedoms," Xenophon said. The senator is seeking to have US-style safeguards that would allow publishers to challenge warrants seeking data relating to journalists' sources.