But the Liberals have labelled the policy a distraction from the Labor's continued opposition to the government's mandatory minimum sentences legislation for serious child sex crimes.

If Labor was to win government in 2022, it would make changes to the Criminal Code to allow for maximum life sentences to be applied to offenders convicted of serious child sex offences against a child and legislate presumptive non-parole periods for these offenders.

Mr Hughes said Labor's position meant courts would be guided by Parliament's view on the seriousness of the crimes.

"We would say it is a vast improvement on any implementation of mandatory sentencing," he said.

He said a maximum penalty was something courts took into account when deciding which sentence to impose.

"The court, when a maximum penalty is increased, sees that as an indication that the crime is to be treated more seriously than previously," Mr Hughes said.

"The courts are already imposing heavier sentences, based on the Sentencing Advisory Council's statistics.

"There is no need for mandatory sentencing ... and making higher sentences available to the courts is a recognised way of Parliament communicating to the courts that certain crimes need to be treated more seriously and to be sentenced more severely."

Attorney-General Elise Archer said the courts already had the discretion to impose the maximum sentence available under Tasmanian law for any crime as well as indefinite detention under Dangerous Criminal laws.

"Labor's policy would do absolutely nothing to change that and would not guarantee convicted child sex offenders go to jail," she said.

"The Hodgman Liberal Government has been pushing for tougher sentencing for child sex offenders for five years and it has been opposed and blocked by Labor at every stage."

Beyond Abuse spokesman Steve Fisher wrote to all members of Parliament on Monday to encourage them to support for mandatory sentencing for child sex offenders.

"The impacts of this kind of offending have often been misunderstood or minimised due to poor community attitudes and a lack of understanding regarding complex trauma," he said.

"As a result, sentences for offenders have often failed to reflect the severity of the crime in Tasmania ... and in many cases perpetrators - including serial offenders - have been given highly lenient sentences."

Labor's justice spokeswoman Ella Haddad said while Ms Archer pointed out the maximum penalty available for serious child sex offences was 21 years, the party wanted the maximum available penalty to be tougher.

Its a proven fact that providing higher sentences for judges means that Parliament intends for those crimes to be treated by the courts as the worst of the worst and attract higher sentences," she said.

The state's Sentencing Advisory Council in a 2015 report said it was unclear whether making changes to the maximum penalties for various offences under the Criminal Code would make a difference to sentencing practice in Tasmania.

"The experience in other jurisdications is that sentences rarely increase in the same proportion as an increase in the maximum penalty," it said.