He said Parliament should allow a conscience vote on legalising gay marriage straight away but if it passed, the result would be contingent on a plebiscite so people knew what they were voting for.

"That would at least deal with the issue one way or another before the next election," he said.

Senator Brandis' offensive underscores the beliefs of pro-gay marriage Liberals and Labor that a push by conservatives for a referendum after the next election was a ploy to delay debate and kill off gay marriage.

Referendum v plebiscite

The Australian Financial Review revealed on Thursday that Mr Abbott has been discussing a referendum with Mr Morrison for some weeks, and was open to a referendum rather than a plebiscite, but had made no decision.

Attorney-General Senator George Brandis has released 34 pages of his appointments. Alex Ellinghausen

It is much harder to effect change with a referendum. A plebiscite is non-binding and to pass requires only a national majority.

A referendum is binding but to pass requires a majority of the states as well as a national majority. Referendums rarely succeed, especially when they lack the support of the prime minister, as a gay marriage vote would.


Mr Morrison told the Financial Review he backs a referendum to change Section 51 (21) of the constitution to insert the words "opposite sex" and "same sex" before the word "marriage".

If passed, Mr Morrison said the Marriage Act would need be amended to bring it in line with the constitution, by removing the definition of marriage as only between a man and a woman.

Scott Morrison backs a referendum to change s51(21) of the constitution to insert the words "opposite sex" and "same sex" before the word "marriage". Andrew Meares

Senator Brandis scoffed at the proposal, saying a referendum to drive a change to the Marriage Act was "entirely unnecessary".

This had been shown by the High Court decision when Senator Brandis intervened to stop the ACT allowing gay marriage two years ago.

"That is an unambiguous, a unanimous and a recent statement by the High Court that the marriage power as currently written is ample to provide the Parliament with the power to legislate for same-sex marriage," he told Sky News.

"There is no doubt whatsoever that an amendment to the constitution is necessary should the Parliament proceed down this path."

Shadow attorney-general Mark Dreyfus backed Senator Brandis.


"Scott Morrison is talking nonsense," he said.

"The constitution leaves no doubt on that subject, and as the High Court helpfully made clear in its decision, marriage has changed depending on how the Commonwealth Parliament has chosen to legislate it at different times, and it can change again."

The MPs willing to cross the floor are Mr Entsch, Dean Smith, Wyatt Roy, Teresa Gambaro, Natasha Griggs and Ken Hogan.

-with Primrose Riordan