Australia’s Prime Minister Tony Abbott has warned anyone planning to marry under a new regional same-sex marriage law to wait for legal action to conclude.

The Australian Capital Territory (ACT) became the first jurisdiction in Australia to pass equal marriage on Tuesday.

However, the Federal Government is challenging the legislation under the instruction of Mr Abbott.

The Liberal Party leader, who remains opposed to equal marriage, told 3AW radio: “If as I think the ACT legislation turns out to be invalid under the Constitution, well then those marriages wouldn’t be valid,” adding: “So I’d suggest to people who would like to be married under the ACT legislation – hold on until its validity is tested.”

Mr Abbott denies his challenge has anything to do with morality.

“It’s not a question of being for or against gay marriage,” Mr Abbott said.

“It’s a question of adhering to the Constitution.

“We are going to challenge this because we think that the Constitution should be adhered to.”

Earlier this week, Christine Forster, the sister of Tony Abbott, revealed that she had proposed to her partner Virginia Edwards.

Ms Forster, a mother of four, said she will only start making concrete wedding plans when she is able to enter a legal union and admits it could be a “long wait”.

Her attempts at changing Mr Abbott’s views on equal marriage have so far been unsuccessful.

“She chews my ear up hill and down dale on this subject,” he said.

“I wish her and Virginia all the best for their future happiness and if there’s a ceremony of some kind, yes I’ll be there with a present. I’ll do the right thing.

“But look, I am a traditionalist on this.

“From time immemorial, in every culture that’s been known, marriage … has been between a man and a woman.”

Equal marriage remains banned at a federal level in Australia and efforts to legalise the measure failed in the Australian Parliament in September 2012.

Australian federal law was amended in 2004 to specify that marriage can only be between a man and a woman.