Nationals candidate Andrew Gee said on Monday that he did not believe the Commonwealth Marriage Act should be changed, but he backed Prime Minister Maclolm Turnbull's plan to hold a plebiscite on the issue if the Coalition was returned to power on Saturday.

Mr Gee said a plebiscite would be a good opportunity for all Australians to have their say.

“The debate needs to be respectful of everybody’s views and I think we are mature enough as a country to do that,” Mr Gee said.

“If the people and communities of the Calare electorate decide that the definition of marriage should change, then I think it would follow that its elected representative would have to accept that outcome.”

But Labor candidate Jess Jennings took a different tack, saying he would be prepared to go against his electorate if a plebiscite found a majority of Calare voters did not support the legalisation of same-sex marriage.

He said he would consult with the electorate but he was personally supportive of marriage equality and the Labor Party under Bill Shorten was supportive as well.

"I don't believe Calare constituents, on a whole, are against it," Dr Jennings said. 

"I don't believe [retiring member] John Cobb's survey results for one second. 

"I would be pleased to canvass community opinion if the Shorten government is elected."

Dr Jennings said he was convinced if all MPs had a free vote in the parliament, it would pass.

"To throw away $160 million on something there has been so much debate on and so much support for already is a waste," Dr Jennings said.

"Taking it to Parliament would be the quickest, cheapest and best result.”

Nick Xenophon Team candidate Rod Bloomfield said he and his party were also opposed to the plebiscite. 

"We support same-sex marriage but we absolutely respect the right of religious institutions to make their own decisions," he said.

"We are talking about changing the Commonwealth Marriage Act and that power is held by parliament.”

Greens candidate Delanie Sky was unavailable for comment.