Barnaby Joyce will challenge Michael McCormack for the leadership of the National Party if the position is spilled in the wake of the sports rorts scandal.
Nationals MPs will meet in Canberra on Tuesday to vote for a new deputy leader after Bridget McKenzie resigned over the scandal.
"If there is a spill then I will put my hand up," Mr Joyce told the Seven Network on Monday.
"I will leave that up to my colleagues. They can make the call."
Mr McCormack is confident he will continue as leader.
Former Nationals leader Barnaby Joyce will stand if a spill is called. Source: AAP
"There is no vacancy for the leadership, at the moment, of the National Party," he told reporters at Parliament House.
"I have delivered for rural and regional Australia."
With Senator McKenzie stepping down as deputy there will be a ballot for her position, but it is up to the Nationals' partyroom as to whether there is a leadership spill.
Mr Joyce, who resigned as deputy prime minister in February 2018, talked up his record as Nationals leader.
"We had the maximum number of cabinet ministers we ever had, we won back more seats than we had in about 30 years, we delivered some big changes," Mr Joyce said.
Labor's agriculture spokesman Joel Fitzgibbon said Mr Joyce's comments amounted to a "vote of no confidence" in the current leadership of the National Party.
"Barnaby Joyce just told us that the National Party is dysfunctional and indeed hopeless. My concern is that a dysfunctional government just got a whole lot more dysfunctional," Mr Fitzgibbon said.
Labor calls for Senate inquiry
Meanwhile, Labor says it will pursue the sports rorts scandal through a Senate inquiry, despite Ms McKenzie's resignation from cabinet.
Senator McKenzie resigned after an investigation by the prime minister's department boss Phil Gaetjens found she did not properly declare memberships of gun clubs that received grants when she was sport minister.
Embattled Senator Bridget McKenzie. Source: AAP
While she did not personally benefit, it was a breach of ministerial standards.
However the Gaetjens report rejected any notion of the grants scheme being used to pork-barrel marginal seats ahead of the 2019 election.
That is despite the use of a colour-coded spreadsheet to designate marginal and target seats.
Mr Morrison said Senator McKenzie - who had provided "great service" as minister, most recently in the agriculture portfolio - had done the right thing by resigning.
Opposition Leader Anthony Albanese said Senator McKenzie had been "thrown under a bus" in order for Mr Morrison to avoid any responsibility.
Labor wants to know more about the role of the prime minister's office in the grants scheme.
The Australian National Audit Office report found: "The evidence available to the ANAO is that representations were received across the three rounds both directly and indirectly, including through the prime minister's office."
"This needs a thorough investigation," Mr Albanese said.
Senator McKenzie said at no time did her membership of shooting sports clubs influence her decision making.
Prime Minister Scott Morrison and then-sports minister Bridget McKenzie. Source: AAP
But she accepted not declaring them was in breach of ministerial standards.
She stood by the idea of ministers having discretion over grants, saying it was "important to our democratic process".
Industry group the Australian Forest Products Association paid tribute to Senator McKenzie, saying the new agriculture minister must strive to equal her "passion for forestry".
"In her relatively short time leading the Agriculture portfolio Senator McKenzie demonstrated enormous passion and understanding for our renewable forest industries," chief executive Ross Hampton said in a statement on Sunday.
