Prime Minster Scott Morrison faces another damaging split over climate policy, with the Nationals preparing to oppose any effort for Australia to join countries cutting carbon emissions to net zero status by 2050.

Under pressure to differentiate from the Liberals, Deputy Prime Minister Michael McCormack declared the proposed target unworkable for the Australian economy, while Former resources minister Matt Canavan warned he was prepared to cross the floor should the Coalition consider adopting the "fantastical" target.