The Turnbull government is confident it will get support from the Senate crossbench to introduce compulsory jail terms for serious child sex offenders.
Justice Minister Michael Keenan has scolded Labor in parliament for its opposition to the proposal, even though it backs every other tough new measure.
The bill, which passed the lower house on Thursday, imposes mandatory minimum sentences for repeat offenders and offences that attract the highest penalties.
Labor argues mandatory sentences let "guilty people off the hook" because juries are less likely to convict them knowing there's no discretion about the sentence and they act as a disincentive for criminals to plead guilty.
Opposition justice spokeswoman Clare O'Neil also fears unintended consequences - such as 18-year-olds in a consensual relationship with a 15-year-old being automatically jailed for engaging in sexual activity overseas.
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But Mr Keenan said that claim - also made by the Law Council - was "absurd".
It was already a crime but no such case had been pursued because federal police and public prosecutors were required to make a judgment as to whether it's in the public interest to investigate and prosecute.
"It's never happened before because there's this discretion within the system, so why will it happen moving forward?" he told MPs.
"It is a complete red-herring."
It was unacceptable that more than 40 per cent of convicted pedophiles don't spend a single day in prison under existing laws.
Labor MPs should hang their heads in shame over their "crazy ideology against mandatory sentencing", Mr Keenan said.
"I think that we will be able to go and negotiate with the crossbench in the Senate to get this bill passed because they are showing a lot more common sense than the Labor party."
On top of scrapping compulsory jail terms, Labor will move amendments in the Senate to increase maximum sentences for a number of offences by five years and propose new aggravated offences targeting those who incite or direct the production of child abuse material.
It believes the additional measures will strengthen the package and better target predators of the worst kind.
