Tasmanian Liberal senator Claire Chandler said this was a disgrace.

An amendment to the Crimes Legislation Amendment (Sexual Crimes Against Children and Community Protection Measures) Bill 2019, which removed mandatory minimum sentences for child sex offences, was supported by Labor, the Greens, Tasmanian independent senator Jacqui Lambie and others in the Senate on Monday.

However on Tuesday, despite originally voting to remove the provision for mandatory minimum sentences, Labor moved away from supporting this amendment in favour of the bill passing.

"As Labor has made clear from day one, our priority is ensuring this bill passes and we unlike the government won't be letting a dispute about one section stand in the way of the other strong, and good measures in this bill," Tasmanian Labor senator Helen Polley said.

Senator Chandler said courts around Australia had lost their way when it came to the sentencing of child sex offenders and it was up to elected politicians to ensure paedophiles ended up behind bars.

"Every week, we read of horrific cases of child abuse and too often offenders are receiving suspended sentences or sentences of less than a year," Senator Chandler said.

"From February 1, 2014, to January 31, 2019, 40 per cent of sentences for Commonwealth child sex offences did not result in a custodial period at all, and of those offenders who did receive a custodial sentence during this period, the most frequent custodial period recorded was just six months."

Speaking in the Senate on Monday, Tasmanian Greens senator Nick McKim said the government had continued its evidence-free ideological agenda of attempting to legislate mandatory minimum sentencing.

"There is research by sentencing experts, by criminologists, by justice experts, that has found that mandatory sentencing actually increases the likelihood of recidivism because, among other reasons, it makes offenders less likely to plead guilty and cooperate with authorities," Senator McKim said.

"To put into shorthand what all that evidence taken collectively shows, people who commit crimes, including crimes against children, don't believe they're going to get caught. Because they don't believe they're going to be caught, mandatory minimum sentences do not play into their thought processes."

Senator Lambie was contacted for comment.