CANBERRA - The Australian government has introduced mandatory minimum sentences for convicted child sex offenders.

The opposition Labor Party on Tuesday evening joined forces with the governing coalition to pass the laws through the Senate.

The laws cover offences that fall out of the jurisdiction of state and territory governments such as those committed overseas.

It increases the maximum penalty for having sex with a child under the age of 16 outside of Australia to 25 years imprisonment from 20 years and introduces a minimum penalty of six years.

Anyone convicted of "sexting" with a person under the age of 16 will face a minimum penalty of five years in jail and a maximum of 20 years.

"The community has an expectation that punishment should reflect the seriousness of the offence, and there are no more serious offences than the type of things this legislation deals with," Attorney-General Christian Porter was quoted by the Australian Broadcasting Corporation as saying.

The Law Council, the peak national representative body of the Australian legal profession, argued it set a dangerous precedent.

"Mandatory minimum sentences are abhorrent to the whole notion of sentencing where judicial discretion is essential and can result in perverse jury decisions of not guilty for low-end offending where juries think the sentencing outcomes will be unfair because of the mandatory minimum," Law Council President Pauline Wright said.

"The Law Council believes that mandatory sentencing erodes an important incentive to plead guilty, which will lead to more contested trials."