Liberal senator Cory Bernardi is reportedly set to split from the Coalition over the coming days, according to ABC News.
Mr Bernardi's office told SBS the South Australian senator would not be making any media comment today, and would not confirm whether he planned to leave the party.
Mr Bernardi set up a group called Australian Conservatives last year and has previously warned he may start a new party for disenchanted conservative voters.
In Canberra, fellow South Australian Liberal senator and education minister Simon Birmingham said he expected Mr Bernardi to stand by recent comments on party unity.
"Every comment I've ever seen Cory make, including over recent months, has been about the importance of Liberals, Nationals, conservatives, all those in the right of centre working together and working as a strong coalition," Mr Birmingham told reporters.
"I believe and I'm confident that Cory is someone of his word."
Treasurer Scott Morrison suggested the South Australian senator was being egged on by others.
"Lets' see what he announces, if he announces anything at all," Mr Morrison told Ray Hadley on Radio 2GB on Monday.
Cabinet colleague Steve Ciobo dismissed suggestions Senator Bernardi's defection would destabilise the government.
"What Australia needs is a strong, stable plan for economic growth and jobs," he told reporters.
Senior Nationals MP Matt Canavan said "of course" he wanted Senator Bernardi to stay in the coalition.
"I love all members of our team and sometimes you don't agree with every member of your team but it's a great team and I hope we keep it together," he said.
Labor frontbencher Tony Burke wasn't surprised about the reports.
"We've been watching a split in the coalition for more than a year now and it's going to continue to unravel," he said.
Speculation about Senator Bernardi's defection comes as voter support for One Nation surged in the first Newspoll of the year.
The minor party garnered eight per cent of the national primary vote - double its Senate numbers at the July election - as support for the government tumbled.
Backing for the coalition has dropped to its lowest level since Mr Turnbull toppled Tony Abbott as prime minister in September 2016.
After preferences Labor leads the coalition 54-46 per cent.
-With AAP
