If the Coalition retains government in Saturday’s federal election, Prime Minister Malcolm Turnbull has committed to his predecessor Tony Abbott’s decision to hold a national poll on legalising same-sex marriage.

Unlike a full referendum, any plebiscite result would not be legally binding and Mr Turnbull admitted this week that backbench Coalition MPs would still be free to vote how they liked.

Mr Broad said in that if there was a plebiscite he would vote in Parliament on same-sex marriage according the answer that gained the most support from Mallee voters.

“I will support the result as determined by the electors of the Wimmera Mallee,” he said.

Mr Broad has been criticised by same sex-attracted people in Horsham for explaining his personal opposition to same-sex marriage by using the example of two rams in a paddock.

"Do I support calling a relationship between a man and a man, and a woman and a woman marriage? No I don't," Mr Broad said in February this year.

"I think a bicycle is not a tricycle and relationships have different names.

"I can put the rams in the paddock and they might mount one another but no lambs will come out."

It was revealed this week that Coalition had started a secret push to hobble any national vote in favour of same-sex marriage.

Under the plan, Members of Parliament and Senators would be allowed to vote against same-sex marriage if their individual electorates had a plebiscite result of ‘no’.

The cost of holding a national plebiscite has been estimated at $160 million.

Labor leader Bill Shorten has pledged to cancel the plebiscite and have a vote in Parliament within 100 days of being sworn in as prime minister.

Labor Members of Parliament and Senators would be required to vote in favour of same-sex marriage.

Labor candidate Lydia Senior said she would, if elected, vote to amend marriage laws.

“I would vote in favour of marriage equality,” she said. 

“It is not up to me to tell other people what to do with their love life and relationships.”

Greens candidate Helen Healy said it was the party platform to support same-sex marriage.

“The Greens have and will vote for marriage equality - every MP, every vote, every time,” she said.

Ms Healy said she had spoken to a large number of people in the electorate and noted the results of a 2011 newspaper poll in the northern Mallee that indicated 64 per cent of people supported same-sex marriage. 

“I believe the people of the Mallee have bigger issues to direct their energies towards rather than worrying about two people who love each other wanting to get married,” she said.

Rise Up Australia candidate Time Middleton said he would, if elected, vote to keep the current definition of marriage.

“My belief and that of rise up Australia is that the marriage between a man and a woman is the most balanced way to raise a child,” he said.

“Every child has the right to a mother and a father.

“This stance will not change so my advice is: if changing the marriage act is high on your priority list then don't vote for me.”

Citizens Electoral Council candidate for Mallee Chris Chris Lahy did not respond to a request for comment.