A new split has opened up within the Coalition over the same-sex marriage plebiscite.

Prime Minister Malcolm Turnbull and Attorney-General George Brandis have said if there is government funding, each side would get the same amount.

But the suggestion that Cabinet might leave the “yes” and “no” sides to raise their own funds has horrified some in the Coalition, including Tasmanian Senator Eric Abetz.

“I wanted to flag my concern up front straight away that this idea that somehow you can have a proper plebiscite without funding for the ‘yes’ and ‘no’ cases would not be the sort of plebiscite that was envisaged by the party room when we decided on it,” he told AM.

Senator Abetz wants the Government to spend at least $10 million for each case, as it did for the republic referendum, and said denying public money would breach the plebiscite deal the Coalition struck last year.

Attorney-General Brandis yesterday gave no guarantee there would be government money.

“We want to keep the cost of the plebiscite as low as it can be kept,” Senator Brandis said.

Attorney-General George Brandis says there is no guarantee of government money. Photo: AAP.

Liberal backbencher Trent Zimmerman told Sky keeping the cost down was important.

“One of the concerns that people raise with me about a plebiscite is the cost of holding a national ballot, so I think it is very important that we try to do everything we can to restrain the costs of the plebiscite when it is held,” Mr Zimmerman said.

Funding to be equal and fair: PM

Another Liberal backbencher Dean Smith has already gone further and revealed he might vote against a bill to set up the plebiscite.

Mr Turnbull is determined to have the national vote, but will only say that if there is government money, it would be the same amount for both sides.

“Any public funding, whatever the nature and terms of it may be, will be scrupulously equal and fair as between the ‘yes’ case and the ‘no’ case as you would expect,” he said yesterday.

“But the nature the extent of any public funding is a matter for the Cabinet’s consideration.”

Senator Abetz had this warning for Cabinet: “Ultimately the plebiscite was a party room decision and I trust that this will remain a party room decision.

“And I trust that Cabinet will ensure that the views of the party room are determined and that the party room is not steamrolled in relation to what is a fundamentally important debate for the future of our society.”

Abbott tight-lipped about original funding plan

Former prime minister Tony Abbott proposed the same-sex marriage plebiscite just over a year ago when the issue was dividing Coalition MPs.

He would not say if his original plan included government funding.

“This is something which will no doubt be discussed in the Coalition party room and let’s wait and see where that discussion goes,” he said.

He would not say what level of public funding he envisaged when he came up with the idea of the plebiscite.

Former PM Tony Abbott won’t reveal his original funding plan for the plebiscite. Photo: AAP.

Labor’s spokeswoman Terri Butler said she was very worried that public money might go to funding a no case.

“He’s talking about publicly funding an argument to say that human rights should not be extended to a minority. That is a significant concern that I have with this,” Ms Butler said.

Opposition Leader Bill Shorten will make a new attempt today to make the plebiscite irrelevant with a private members bill to change the marriage act by vote of MPs.

Crossbench MPs will bring in their own version.

– ABC.