Liberal National Party Senator Barnaby Joyce would be hesitant to support optional preferential voting because it disadvantages smaller parties.
Some senior Liberals reportedly want to change electoral laws to allow a system where voters would not have to number the ballot and give preferences to candidates they may not support.
The Australian newspaper has reported they believe this will hurt the Greens and Labor, but Senator Joyce said that may not be true in the long term.
"Optional preferential voting works in your favour when you are the predominant party on one side or the other of the political debate, whether that's the left or the right," he told reporters in Brisbane on Thursday.
"But when you have to share that limelight with someone else, it works against you."
He pointed to Queensland where he said former Labor premier Peter Beattie used the preferential system to disadvantage the Liberal and National parties.
"What might work in some instances won't work that way all the time, and certainly won't work that way in another part of the country," Senator Joyce said.
"So I'd be a little bit more hesitant in endorsing an optional preferential voting pattern because it might work for you today but next year it won't."
Opposition electoral affairs spokeswoman Bronwyn Bishop has told The Australian it should be considered because it would lessen the informal vote.
But acting opposition leader Warren Truss has dismissed suggestions the coalition is moving to change the present system.
"The coalition has no plans or policy to change the current system of compulsory preferential voting," Mr Truss told Fairfax Media.
Labor has rejected suggestions the federal electoral laws should be changed, with Special Minister of State Gary Gray telling AAP the system shouldn't be tampered with for partisan advantage.