Nationals senator Matt Canavan says he will vote against a net-zero emissions target if it was brought to parliament, labelling the climate debate a "distraction".
Prime Minister Scott Morrison has not yet committed to achieving carbon neutrality by 2050 but is laying the groundwork to adopt it as policy, following allies such as the United States.
Senator Canavan, who is a staunch advocate of coal-fired power and the mining industry which is a major employer in Queensland, said it was a "mythical target".
"I am opposed to it," the former minister told the ABC on Monday.
"I can't stop a government signing a piece of paper. But as a senator for Queensland, I'll make sure that all my votes in the parliament represent their interests."
Asked whether he would cross the floor in the Senate, he said: "Absolutely I would, if that was in the best interests of Queensland."
He said the exclusion of agriculture - which is being discussed within the Nationals as a bargaining chip with their Liberal colleagues - would not change his approach to the issue.
"Let's focus on real things - I find this a massive distraction," Senator Canavan said.
Excluding agriculture would put Australia in line with New Zealand's net-zero by 2050 plans, which places a lower target on reducing methane levels.
Agriculture made up 13 per cent of Australia's greenhouse gas emissions last year and the percentage is expected to rise to 2030 as the effect of the drought eases.
Greens leader Adam Bandt said on current trends Australia was set to heat by a catastrophic four degrees during the lifetimes of today's primary school students.
"Climate change is already hurting people who are putting food on our table," he said.
"It's making it harder to access water, throwing crop seasons into disarray, and supercharging heatwaves that cook produce on the vines."