Prime Minister Tony Abbott says his government will mount a High Court challenge to the ACT's proposed same-sex marriage laws to ensure the constitution is "adhered to".
The territory could have gay marriage ceremonies by December if legislation passes its assembly, as expected, later in October.
But Commonwealth Attorney-General George Brandis on Thursday confirmed the government will challenge the laws in the High Court, warning that same-sex couples could be distressed if their marriages were later invalidated.
Questioned about the government's motives for the threatened High Court action, Mr Abbott said on Friday it was "pretty clear" the commonwealth had constitutional responsibility for the country's marriage laws.
"We think it is important that there be a uniform approach to marriage around the commonwealth, and that's what we are going to do our best to ensure," Mr Abbott told reporters in Darwin.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"It's simply a question of the constitution. The constitution provides that the commonwealth parliament shall have the power to make laws for peace, order and good government of the commonwealth with respect to marriage.
"Now that's a provision that's been in our constitution since 1901, there is no proposal to change that (and) it's important to ensure that the constitution is adhered to."
