Attorney-General George Brandis confirmed the High Court challenge to the laws on Thursday, after informing the Chief Minister and ACT Attorney-General Simon Corbell in a phone call on Wednesday night.

Ms Gallagher said she had not spoken to Mr Abbott since the federal government announced its plans to challenge the legislation because it was “a threat” to the “well-established position” that marriage was a Commonwealth matter.

“Certainly [Senator] Brandis made it clear he was acting on instructions from the Prime Minister,” Ms Gallagher said.

“I don’t need to speak to Tony [Abbott] … Certainly it was made very clear the instructions were coming from him.”

Comment has been sought from the Prime Minister.

Mr Abbott told reporters in Darwin 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," he said.

"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."

But Ms Gallagher said the federal government was making a “convenient” argument about process to avoid arguing the true point.

“They don’t want to play the issue,” she said.

“Because I think they probably understand that community sentiment [on same-sex marriage] has changed.

“When you can’t argue the point, you argue the process.

“Sure, let’s have that tested but I think it does avoid the more difficult position that people don’t want to articulate: that is that they don’t like same-sex marriage, which is what it comes down to at the end of the day.”

The ACT’s same-sex marriage bill is expected to pass through the Legislative Assembly later this month.

with AAP