Malcolm Turnbull refuses to rule out free vote on same-sex marriage, but Barnaby Joyce says there will not be one

The government cannot propose a free vote on same-sex marriage now the plebiscite is doomed because it would breach the Coalition agreement, conservative MP George Christensen has said.

The chief nationals whip made the comment on Sky News on Thursday, as Nationals MPs that oppose same-sex marriage began a campaign to prevent reconsideration of a free vote now Labor has said it will vote the plebiscite down.

It comes after Malcolm Turnbull refused to rule out a free vote on marriage equality, in direct contrast to the stance taken by Nationals leader Barnaby Joyce.

Joyce said there was no possibility the Liberal and National Coalition could split over same-sex marriage.

“We have a strong Coalition, it is quite clear that we have a promised at the election fora plebiscite,” he said on Thursday.

Asked about MPs claiming no free vote was possible under the Coalition agreement, Joyce said “don’t make threats, have people understand clearly who you are”.

Marriage equality: Malcolm Turnbull won't rule out a free vote for Coalition MPs Read more

On Wednesday Christensen said: “All I will say on that is if all of a sudden the policy becomes a free vote, my firm view, and it’s not just a view it’s actually the reality, [is] that is breaking one of the tenets of the Liberal National Coalition deal.”

“That would be quite a serious matter so I don’t think that’s going to eventuate.”

The prime minister has himself publicly acknowledged in an answer on ABC’s Q&A on 21 June that the Coalition agreement “states a commitment to the plebiscite which was the government’s policy”.

On Wednesday a spokeswoman for the prime minister confirmed the Coalition agreement states a commitment to the plebiscite, but would not say whether changing the policy would breach the agreement.

She referred to Turnbull’s response at a press conference on Wednesday urging the Senate to pass the plebiscite bill. Turnbull said it is the government’s position to hold a plebiscite but repeatedly refused to rule out holding a free vote on same-sex marriage.

A spokesman for Joyce said “people have different interpretations of the Coalition agreement” about whether it is just the agreement between the Liberal and National parties or includes joint policy commitments.

“There is nothing in the Coalition agreement that contradicts the policy taken to the election. The policy is the agreed position: that we will hold a plebiscite.”

Joyce’s spokesman said the agreement contained nothing more extensive than the policy commitment to the plebiscite. It therefore does not deal with what happens in the event the plebiscite is blocked, although he said that did not mean everything was on the table.

On Radio National Drive on Tuesday deputy prime minister Joyce ruled out a free vote. When pushed if the party room could revisit its policy after the plebiscite was voted down, Joyce said it would be “chaotic” to do so.

“The position is this: if you wish to change the Marriage Act, then support the plebiscite,” he said.

“If you don’t, then there is no surety whatsoever that there is going to be any changes to the Marriage Act, and then it becomes an issue for a future government.”

Joyce denied he was at odds with Turnbull, and said that “Plan B” was not to pass same-sex marriage by another means but rather to deal with other issues first.

Responding to comments from Nationals MP Andrew Broad that he would withdraw support for the government if there was a parliamentary vote on marriage without a plebiscite, Joyce said the comment was “not helpful”.

After the plebiscite bill is defeated, supporters of same-sex marriage in the Coalition could seek to use Tony Abbott’s assurance that the 44th parliament would be the last in which Coalition MPs are bound on the issue to argue a free vote should be held.

Long-time marriage equality advocate Rodney Croome said “regardless of the exact wording of the agreement between the Liberal and National parties it is unconscionable for Nationals MPs to hold Malcolm Turnbull to ransom over a plebiscite”.

“Mr Turnbull has done everything he could reasonably be expected to do to get a plebiscite up and it won’t be his fault if the Senate blocks it,” he said.

“Smart Coalition MPs would quietly welcome the increasingly toxic plebiscite being blocked and then move to the free vote that most Australians want.”

Croome warned Australians would “punish opponents of marriage equality at the ballot box if they keep blocking a free vote”.

Australian Marriage Equality co-chairman Alex Greenwich told Guardian Australia “there are strong and genuine supporters of marriage equality in the National party, members who are undecided and those who are opposed”.

Advocates would now focus their efforts on those that are undecided to give them a “better understanding” of the issue, he said.

Asked about Joyce’s comments, Greenwich said “this is one issue where people can comfortably change their minds – as a majority of Australians have”.

“I see this as an opportunity, not a challenge.”