Nationals leader David Littleproud will face a challenge for his position following the party's divorce from the Liberals.
Backbench MP Colin Boyce, who represents the Queensland electorate of Flynn, said he would launch a spill motion against Mr Littleproud in the coming week.
The move, announced on Wednesday, followed the Nationals walking away from their coalition partnership with the Liberals over hate-speech laws.
Mr Boyce will run for the party leadership at a meeting due to take place on Monday.
He said the coalition needed to reunite if the party was to have any chance electorally.
"We do have to get this coalition back together again. It's a bit like trying to weld square pipe to round pipe," he told Sky News in announcing the spill motion.
"The reality is, they follow the course they're on now we are going over the political cliff.
"David has made some bad decisions recently. He's upset just about everybody you can possibly upset."
Earlier on Wednesday, before the spill was announced, Mr Littleproud said a split with the Liberals was not what the party wanted.
"We didn't leave in anger, we left in disappointment," he told Sky News.
"I can reconcile in my head every day that we've made our decision on principle, and I'm proud of our room and how we got to that decision, but we're pragmatic and calm about what we can do moving forward."
Mr Boyce said a reunion with the Liberals was needed to avoid a political wipe out.
"The National Party is committing political suicide by removing itself from the coalition. The National Party now faces a right-flank onslaught from One Nation," he said.
"There is a huge surge up here (for One Nation). There's lots of people say to me, you know, 'you should join One Nation' and so forth."
Former Nationals MP and deputy prime minister Barnaby Joyce defected at the end of 2025 to join One Nation, as Pauline Hanson's party rides high in the polls.
The most recent Newspoll showed One Nation with a 22 per cent primary vote, compared to the former coalition at 21 per cent.
It was the first time the far-right party had greater supporter than the coalition in the poll's history.
